As a result of its location in the Sonoran Desert, Phoenix has a hot, dry climate and is pretty much sunny all year round. In fact, Phoenix receives the most sunshine of any major city in the world. Despite being dubbed the ‘Valley of the Sun’, Phoenix actually has four seasons, even though the transition between them is rather subtle. Most importantly, though, new arrivals moving to Phoenix must prepare for a climate of extremely hot and humid summers and mild winters.
The weather in Phoenix is hot and dry, and the sun is out for much of the year thanks to the city’s Sonoran Desert location. It is often ranked the sunniest major city in the world. Despite being dubbed the ‘Valley of the Sun’, Phoenix actually has four seasons, even though the transition between them is rather subtle. New arrivals should prepare for extremely hot summers and mild winters.
In summer, temperatures can reach up to 110°F (43°C). Averages are around 100°F (38°C). Unlike most desert locations, which experience drastic temperature fluctuations between day and night, evening temperatures do not drop that noticeably in Phoenix because of the urban heat island effect.
Although rainfall is minimal throughout the year, humidity is higher during the summer months, when the North American monsoon arrives. The extra moisture can also contribute to flash floods, destructive winds, dust storms, and lightning. In a strong monsoon, a haboob (a towering wall of dust) can sweep across the valley, and visibility drops to almost nothing.
Phoenix is in Maricopa County, which has some of the highest ozone pollution levels in the US. Ozone forms in sunny climates, and Phoenix is particularly prone to it. As Phoenix grows and more people drive, vehicle emissions add to the problem. People with respiratory conditions may find the city’s air quality hard going, especially in the summer ozone season.
There is a different issue in winter. Temperature inversions are common: warm air is above the cooler air near the ground, so wood smoke and other particulates cannot disperse. To keep the air clearer, Maricopa County issues ‘no burn day’ advisories.
Although the surrounding mountain tops may receive a dusting of snow, winters in Phoenix are largely pleasant. The winter average is around 54°F (12°C). Many newcomers come to relish the cooler months: the weather is milder, and the summer ozone haze has cleared, so the skies are often a bright blue.