The places with the least variety of weather are all within a few miles of the Pacific Ocean. Most are in California.
The city with the least variety of weather is San Francisco, CA. San Francisco is located in a unique location on the end of a narrow peninsula surrounded on three sides by water. San Francisco averages only 2 days per year above 90 degrees, and less than one morning per year below 32 degrees. Temperature-wise, it is hard to tell the difference between summer and winter. Both are cool and there is also little difference between morning and afternoon temperatures.
It should be noted that around most of these costal California locations, there is a large amount of variation within a short distance. Average precipitation and temperatures can vary a lot within only a few miles. But this study was done to find the places with the most variey of weather in one location. Also, the Weather Variety Index is a function of the weather in one location. A place nearby that is always warmer or cooler or wetter may have a similarly low Weather Variety Index.
The west coast has a relatively small variety of weather (compared to the central plains) because of the Pacific Ocean. Water has a very high specific heat, and does not change temperature very quickly. Pacific Ocean water temperatures in the summer are not much warmer than in the winter. Consequently, west coast locations do not have a very large seasonal temperature variation. In the summer, the cool temperatures at the surface make the air very stable. While spring and summer afternoon thunderstorms are common in the east, they are rare on the west coast. In the winter, the ocean keeps costal areas relatively warm, making snow rare on the west coast. In fact, El Paso on the Mexican border averages more snow than Astoria on the extreme northern coast of Oregon. Large hail and strong tornadoes are also extremely rare on the west coast.
These places with the least variety of weather also tend to have the most comfortable weather. But the Weather Variety Index does not deal with comfort. That will be the subject of the next special climate report coming soon!
Diurnal Temp. Variation
Annual Temp. Variation
Complete Alphabetical List: Where does your city rank?