Phoenix is famous for its scorching hot temperatures during the summer. Between June and August, the daily high temperatures can be over 110°F (43°C) for several days in a row.
So, why is Phoenix so hot? There are a variety of natural and man-made factors.
1. No Sea Breeze
This might seem kind of obvious, but I'm going to cover it anyway. Many of America's major cities are coastal cities. San Francisco, Los Angeles, Seattle, NYC, Miami, and Chicago are all located near the ocean.
The effect of wind blowing across the water provides a year-round cooling effect called a Sea Breeze. Because Phoenix is not located near any large bodies of water, the city does not receive this natural cooling effect.
2. Low Elevation
Another factor in a city's temperature is its elevation. Phoenix is about 1,080' above sea level. Compare that with cities like Las Vegas (elev. 2,030'), Salt Lake City (elev. 4,327'), Denver (elev. 5280'), or Albuquerque (5,312'). Lower elevations typically have higher temperatures because there is more air above them, which increases the atmospheric pressure.
3. Close to the Equator
You may recall from high school geography class that the world is divided into a system of vertical and horizontal lines called Latitude and Longitude.
Phoenix is relatively close to the Equator, at just 33°N Latitude. Las Vegas is at 36°N, Salt Lake City is at 40°N, Chicago is at 41°N and Minneapolis is at 45°N. (Keep in mind, the North Pole is at 90°N).
Near the Equator, Earth's atmosphere is very thin. This allows more of the sun's energy to be absorbed by the earth. Higher elevations are more protected against the atmosphere and thus have cooler temperatures.
4. Down in the Valley
Phoenix is located in the Salt River Valley - a low spot surrounded by mountains. These mountains block the wind and rain that would ordinarily be transported by a current of fast-moving air called the sub-tropical Jet Stream. Because of our natural barriers, Phoenix has over 300 days of sunshine per year.
5. The Heat Island Effect
Some of the factors in Phoenix's notoriously hot temperatures are due to man-made causes. One of these is the heat island effect.
Much of the city is paved with concrete and asphalt for roads, parking lots, driveways, and sidewalks. Pavement stores and retains the heat from the sun. What this means is that after the sun goes down, overnight low temperatures do not drop much as they would in an unpaved area.
So there you have it: five reasons why Phoenix is such a hot city during the summer.
Also, please remember that this article covers the climate of Phoenix. Other cities in Arizona including Flagstaff and Show Low have all four seasons.