Thursday, January 20, 2011

The Perfect Climate - Part 2

by Conroy

In Part 1 I detailed my climate formula and the ranking of U.S. metropolitan areas. In this post I want to explore the rankings in more detail, highlighting some interesting aspects.

Los Angeles has a "perfect" Mediterranean climate (Koppen)
My rankings make no reference to existing climate classification systems, such as those by Koppen and Thornthwaite. This is intentional. These standard systems are designed to classify global climates, identifying very large areas by temperature, precipitation, flora and fauna, prevailing winds, etc. This is absolutely legitimate, and I really like the Koppen regime that provides major climate groups (tropical, temperate, polar, etc.) and various sub-groups based on annual precipitation, temperature ranges, and seasonality (among other characteristics).

However, there are two major reasons I chose a different approach. First, I'm interested in where it would be most comfortable to live and/or spend a lot of time, which I think is primarily based on temperature and not other climate characteristics such as precipitation. All aspects of climate matter deeply in the various Earth sciences and maybe even economics, but not necessarily in livability. Second, because these systems are global in scale, they group vast areas together with insufficient differentiation. According to Koppen, Baltimore (my hometown) falls under the Humid subtropical classification, but so does Brownsville, Texas. As my rankings show, Baltimore and Brownsville experience very different climates (mean January temp.: 37 degrees and 60 degrees, respectively). For practicality, we need a system that is more specific.

Humidity and Precipitation
I touched on this above and I discussed it briefly in Part 1. However, I received a couple of comments from readers who felt that humidity and precipitation should be more of a factor (or a factor) in the climate rankings. Again, my position is that at the extremes, such as high humidity coupled with high temperature or extremely low annual precipitation, these climate characteristics can certainly be important. That concession aside, in general, in the United States, the benefits of indoor climate control (both in buildings and in vehicles), extensive irrigation and landscaping in dry areas, and seasonal variations in humidity and precipitation patterns, all work to mitigate the discomfort of high or low humidity and/or precipitation. As Celeste from North Dakota commented to Part 1, "...back to the issues of heat and humidity...I would go for these places [San Diego or Jacksonville] - humidity or not - before choosing a place like Minot [North Dakota] where I could literally freeze to death 8 months of the year."

Patterns - The Coastal Effect
I'm hardly writing anything original when I note that proximity to the ocean has a moderating effect on temperature and temperature variation. Hence coastal areas tend to score higher in the climate rankings than places at the same latitude (and elevation) further inland. The West Coast, consistent with west coasts all over the world, has a milder climate than the east, and the mild climate extends all the way to Canada (and beyond). Seattle (14.2 climate score) has a far milder climate than say Milwaukee (-6.5 climate score) despite being located about 300 miles farther north. Perhaps the best example on the West Coast is Coos Bay, Oregon (17.1 climate score), located southwest of Eugene, Coos Bay has as good a climate as Fresno, California (17.3) or Macon, Georgia (17.0), both located several hundred miles farther south. 

The Outer Banks
The pattern is the same on the East Coast, but the temperatures (both mean and variance) are more extreme - as is the weather in general (the Atlantic and Gulf coasts are subject to hurricane strikes every summer and autumn). Perhaps the most interesting location is the Outer Banks of North Carolina. For instance, Hatteras Island (climate score 21.6) has a significantly higher climate score than places immediately to the west on the mainland coast like Jacksonville, NC (16.8) and Elizabeth City, NC (15.8), and as high as  locations much farther to the southeast like Savannah, Georgia (21.8) or "hot" places like Tucson, Arizona (22.0).

Patterns - The Elevation Effect
I've noted the effect that elevation has on climate in my earlier post about climbing to high places, and nowhere is that fact better exemplified than in the state of Arizona. The northern and eastern three-quarters of the state are generally at elevations of 3,000 feet and higher (the Grand Canyon is over a mile deep in places). Meanwhile the western and southern quarter of the state is much lower. Phoenix, situated along the Salt River in the "Valley of the Sun", is only about 1,200 feet above sea level, and Yuma in the far southwest corner of the state lies on the Colorado River only 200 feet above sea level. As a result, Phoenix and Yuma are warm in winter (generally) and blisteringly hot in summer. Phoenix's annual mean temperature is 74 degrees, one of the highest in the country, and summer highs average well over 100 degrees. (More on the deceptively unattractive Phoenix climate below.)

Palm-lined street in Phoenix
Snow in Prescott
Meanwhile, just 100 miles to the north of Phoenix is Prescott (the original capital of Arizona Territory), which sits at 5,400 feet above sea level. There it's cold in the winter (see the snowy picture to the right) and mild in the summer, mild for Arizona anyway. The annual mean temperature is 54 degrees, 20 degrees lower than Phoenix. Just 100 miles, but 4,200 feet of elevation, results in substantially different climates. Another 50 miles north and 1,400 feet higher in elevation is Flagstaff where there is a genuinely cold climate. The annual mean temperature is just 46 degrees. In few places in the United States will you find such distinctly different climates in such a short distance, emphatically underscoring the relationship between elevation and temperature.

Florida and California
Orlando at night
The two continental states that enjoy the best climates are clearly Florida and California. Together they occupy 19 of the top 23 places in the rankings, including 12 of the top 13 (Honolulu, little surprise, gets the top spot). First, it's important to note that both states have a lot of people - think this somewhat attributable to their climates? - which means that they both have a lot of metropolitan areas. If Hawaii was bigger with more people, it would dominate the top of the rankings. But accepting that, these states have great climates because they benefit from geography.

Florida is located farther south than any other state, but larger portions of Texas are just as far south as most of the Florida peninsula. However, Texas does not enjoy the moderating benefit of two warm bodies of water acting as "blockers" preventing cold air from penetrating the Florida peninsula during winter. The Gulf of Mexico and Atlantic Ocean also keep Florida's temperature somewhat moderated in summer. Cold snaps are possible, especially in north and central Florida, and summer is hot and humid, but all-in-all, Florida greatly benefits from being surrounded by water. Want more proof, consider the climate of Fuzhou, China, which is located at about the same latitude as Miami in southeast China. It's much cooler than Miami though because cold continental weather, not moderated by warm water, affects the area during winter.

San Diego harbor
California has other advantages. The lowing lying coastal areas are (1) protected from cold continental air by high mountains to the north and east, and (2) benefit from the cool Pacific which moderates year-round temperatures. The results is lots of sun and comparatively moderate temperatures all year long. The Central Valley gets lots of sunshine and being removed from the Pacific it sees higher summer temperatures and lower winter temperatures than the coast, but also benefits from the high mountains along the eastern border of the state, which help to deflect cold continental air. The net result is a really pleasant climate in most of the heavily populated areas.

Unexpected Results
As I compiled these rankings, I was surprised by the result for two major cities, Phoenix and Las Vegas. The impression I had of Phoenix was that it was a great climate, sure it is hot in summer but that's why there is air conditioning. After all, lots of people seem to retire to the greater Phoenix area, which for decades was one of the fastest growing big cities in America. However, I think this is something of an illusion. Phoenix is mild in winter, with highs in the 60s and 70s and lows in the 40s. But in the summer it is just too hot. From June 1st through September 14, the mean high temperature is at least 100 degrees, and June through August the mean temperature is over 90 degrees. That's just unbearable, and I say that as a person who likes heat. It must be impossible to spend time outdoors in the summer sun. As a result, Phoenix's climate score is "just" 21.0, ranking 11th out of the 30 largest metropolitan areas in the United States. Phoenix's climate is more like that of Riyadh and Baghdad than Los Angeles.

The arid Las Vegas valley
Now Las Vegas gains its reputation as an adult playground for reasons largely separate from the climate. However, the fancy resort/casino pools and palm-lined streets would give the impression of a fine climate. This really isn't the case. I've been to Las Vegas twice, the first time was Labor Day weekend 2007. The temperature was meltingly hot, with highs way over 100. I couldn't walk along the Las Vegas Strip for long. The second trip was in late April 2009, and I arrived to mid-day temperatures in the 50s (it did warm up over the next couple of days though). These experiences highlight the fact that Las Vegas is colder in the winter and hotter in the summer than may be commonly believed. Winter lows are in the mid-30s, and I bet it would receive more snow if it wasn't located in one of the driest parts of the country. The city's climate score is only 13.0 (that's not much better than Baltimore - 9.9), and ranks just 16th out of the 30 largest metropolitan areas in the United States.

Rankings at the Extremes
In developing these rankings I surveyed all major cities as well as some smaller places at geographically interesting locations to get a sense of the climate at elevation, latitude, and other extremes.

Leadville at over 10,000 feet elevation
Leadville, Colorado is located southwest of Denver, but at an elevation of over 10,000 feet; one of the highest towns in the U.S. As a result the weather is cold, and the climate score is a bone-chilling -20.0, practically the same as Fargo, North Dakota.

Badwater Basin - the lowest, hottest spot in North America

Conversely, Death Valley, California is the lowest spot in North America. Badwater Basin is situated 282 feet below sea level. Death Valley is the hottest place in North America and one of the hottest places on Earth. The July mean high temperature is deadly 115 degrees, and July mean temperature is over 100 degrees! It's climate score is 12.3, which is probably generous (I didn't account for super-extremes like this).

Idyllic Key West

Key West, Florida is located farther south than any other city in continental U.S. It also has the best climate. The mean January low is 65 degrees and mean August high is 90 degrees. Idyllic. The climate score is 47.3, nearly as high as Honolulu (48.3).

Hilo - the highest rated climate in the U.S.
Hilo, Hawaii is the largest city on the Big Island. It has the sunny distinction of having the highest climate score of any city that I surveyed at 53.2. It's like an even less variable version of Key West. Because of it's location, I would also suggest that it's one of the least visited cities on my rankings.

Barrow, Alaska on the other hand has the gloomy distinction of having the lowest climate score (by far) of any city that I surveyed at -48.8. It surely looks forlorn (see the picture). In February, the mean temperature drops to -16 degrees. It's somewhat hard to believe that the record low is "just" -56 degrees. Imagine spending the dark polar night in Barrow for the winter...what a horror.
Barrow during the winter twilight - the worst climate in the U.S.

The East is not without it's cold areas. Upstate Maine is thinly populated and probably even less thought about. But cities like Caribou and Jackman have climates just as extreme as Fargo and Grand Forks, and in great contrast to coastal cities like Portland.


I'll return to theme of climate in the future, discussing other parts of the globe. Until then, look for a new climate page that will include much of the data cited in these two posts.

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  1. Conroy, I couldn't agree with you more about Phoenix. I moved there a couple of years ago from Manhattan. It was February when I arrived and the first day it was bright sunshine with temperatures in the high 70s. I thought, not bad. Then the summer came. I remember July 4, I was supposed to go to a coworkers cook-out. When I walked outside in the early afternoon, it was like 115 degrees - in the shade! I started walking to my car, and then I just turned around and went back into the house. I've experienced two summers so far and can safely say that they are far worse than New York winters. I don't think that I will complain about winter cold ever again.

    Scott, Mesa, AZ

  2. Scott and Conroy,

    I won't argue that the Arizona weather is really hot during our long summer (I live in Tucson), but I would take that any day over a long and cold winter. I came the Arizona from Minnesota for school and stayed. My first summer was a shock, but I can tell you first hand that the heat is way better than the northern winter.

  3. Ill have to be honest with you about the florida climate. I've lived in florida for about 12 years (in the tampa area) and the climate is nothing to strive for. The summers are absolutely brutal. April- October you have to deal with temps above 90F with a lot of humidity. Its not the heat as much as it is humidity. Every summer morning i always walk my dog. In the morning its about 86F with usually 90 percent humidity. 5 minutes outside and your pouring with sweat. But the winters are fine. Here in the tampa bay area you get about 3 weeks out of the year where high temps are below 60F and about 5 nights where it drops below freezing.

  4. Anonymous,

    Thanks for your comments. I've received several comments that support your points. Humidity does affect the enjoyment of a climate, especially when coupled by high temperatures. I seem to be less bothered by heat and humidity than some others, and I would gladly trade my Maryland winters for your Florida summers. However, not living there, I must respect your judgments. Can I ask where you lived before Tampa? What are you thoughts on the climate in your previous home?

    The Man lives in South Florida, and relocated from colder areas, so I would be curious to get his thoughts on the pros and cons of the climates in the locations where he's lived.

  5. Barrow's quite beautiful if you give more than just a cursory glance at the surface, but then I enjoy the cold. I think it's spectacular in the winter, but you'd be surprised how much life and color there is in the tundra in the summers. I was born and raised there, hunting, snow-machining, sledding on the bluffs in the winter, beachcombing, watching the whaling, having picnics along the coast in the summer watching an hours-long sunset spanning a 360 degree horizon with nothing to obstruct it. A horror? Hardly!

  6. Anonymous,

    I'm a warm weather lover so Barrow would be challenge for me to enjoy, even in the summer. I also think the extreme fluctuation between summer light and winter dark would get to me.

    That said, I don't doubt there is beauty in Alaska's arctic far north. I would love to see the Arctic Ocean during the summer solstice with the sun circling around the sky. I also would love to witness the brilliant Aurora Borealis.

    In any case, it seems the climate is perfect for you, which probably means you should invert my rankings to match your tastes.

    Enjoy the upcoming summer and thanks for your comment!

  7. I lived in Leadville Co. for 11 years and it was wonderfull. Peacfull, beutifull, and amazing. Still dream about it today. I,ve lived in Wisconsin, Alaska, Arizona, Washington, and parts of Europe. I will take the cold over blazing hot heat any day of the week. I can always get warm when i'm cold (ad more layers and move around to get the blood flowing), but when its 110 degrees outside, its just plain miserable. Just an opinion so take it for what its worth. every place has its own diamonds in the ruff. its up to you to find whut urs are.

  8. Anonymous,

    Thanks for your comments. I have to admit a certain jealousy regarding the variety of places where you have lived.

    It's true that you can combat the cold in a number of ways, but many years ago I drove through Leadville in mid-July. It was afternoon, but the temperature was only in the low 50s. That's just nothing like summer to me. However, at least Leadville has the mountains, which offer some terrific year-round recreational opportunities.

    You're certainly correct that extreme heat can be enervating and even dangerous, and the summer weather in places like Phoenix is as unrelenting as the winter cold in places like Green Bay, Wisconsin.

    However consider this. I am reading Edward Gleaser's new book The Triumph of the City. In it he confirms one of my suspicions; over the last century, no variable has been a better indicator of urban growth in American cities than temperate winters. People seem more willing to endure the oppressive Phoenix summer than the frigid Detroit winter.

  9. Here's an interesting fact. Yesterday (5/15), the nation's high temperature of 98 degrees (F) was recorded in Bullhead City, Arizona, which is located on the Colorado River just a little south of Las Vegas. No surprise there.

    However, the nation's low of 25 degrees was recorded in Grand Canyon, Arizona less than 150 miles away (and also on the Colorado River, but high above it).

    More than a 70 degree temperature difference in such a short distance. Again demonstrating the effect of altitude on temperature and another illustration of the varying Arizona climate.

  10. Conroy,

    I am well aware people seem to thrive for mild winters. It is also true that because the landscapes of hotter regions have not been affected by glaciation, there is much more flat land, which to me is why so many people move to climates that to me are utterly appalling.

    I think the local summers in Melbourne, Australia at 26˚C (80˚F) are on the warm side, and always say to people that Tasmania has the best weather in Australia - not because it’s cold (which it isn’t) but because the summers are so cool at 22˚C (70˚F). 22˚C is cooler than summers in most major cities of Canada, and to me the best climate in the US in in the thinly settled coast of Oregon and Northern California, say North Bend or Crescent City. Although it is rather wet there (nothing compared to say Ketchikan, mind you), the temperatures at a relatively constant 15˚C are just perfect and there is a short dry period to provide contrast. I cannot myself call the winters in Florida or lowland Arizona even “temperate”, rather I would call them warm shorts weather. Even with its very cold nights, Flagstaff for me is a vastly more pleasant climate than Phoenix or Tucson: the daytime average for the year is just perfect at 16˚C (60˚F) though the nights are really cold.

    In fact, I despair and fear of living in the extremely cold weather of Canada or Siberia, but nonetheless I think that climates as hot as Florida or lowland Arizona should be rated much, much worse than they are and that climates with really cool summers, as long as their winters are not brutal, should be rated much better.

  11. JP,

    Thank you for your comments. Sorry for being a little late with a reply, but I've been away for the last week.

    Your perspective is one shared by many readers. Preference for cooler (moderate) temperatures or even colder temperatures is a matter of taste.

    I am going to follow-up on this post (this week) by examining how a modified rating system would affect climate rankings. Again, the system I developed can be applied to anyone's tastes by modifying the "quality points" assigned for different temperature values. Such a modified approach may rate San Francisco well ahead of Miami.

    In addition, I'll provide the climate scores for many international cities (including Hobart and Sydney).

    Thanks for reading and keep an eye out for my next post.


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  14. Conroy, that is a sensible system to do. I generally use an ideal base at around 16˚ to 17˚C or 60˚ to 62˚F maximum temperature - perhaps I little higher to provide contrast. I also think there could be formula for precipitation. If you doubt this, consider for yourself who would want to live in a place as wet as Ketchikan, Alaska or Owase in the Kii Hantō of Japan or Baguio in the Phillippine mountains or Mahabaleshwar in the Western Ghats??

    In both cases, I firmly think there is a need for asymmetry so that the climate index falls more rapidly moving to hotter and wetter climates than to cooler and drier. A very dry climate is not necessarily uncomfortable, whereas a very wet one can be cumbersome to get around especially if there are extremely wet months or consistent rainfall or year.