Phoenix Climate Trends
Arizona · US States · 50 years of climate trend data
This page tracks how Phoenix's climate has shifted over 50 years of daily measurements, warmer summers, milder winters, and changes in rainfall, rather than current conditions. The two clearest signs of change: extremely hot days have grown by 14.4 a year and frost days have dropped by 3.8 a year, from 5.2 to 1.4 days below 0°C. Measurement period: the last 50 years (1976-2025).
Data through September 12, 2026.
Frequently asked questions about Phoenix's climate
How much warmer have summers in Phoenix become?
The average daytime high across June, July and August rose by 0.4°C between 1976-1980 and 2021-2025. That is a five-year average at each end rather than two isolated summers, so a single exceptional heatwave or cool summer does not drive the number.
Have winters in Phoenix become milder?
The average daytime high across December, January and February rose by 1.6°C between 1976-1980 and 2021-2025. In many capitals in this dataset winter is changing faster than summer, which shows up most clearly in the frost-day count below.
How many days above 30°C does Phoenix get a year?
Phoenix averaged 192 days a year above 30°C in 2021-2025, up from 177 in 1976-1980. These are the days that set peak cooling demand and the days hospitals see heat complaints rise.
How many frost days does Phoenix still get?
Phoenix averaged 1 frost day a year in 2021-2025, down from 5 in 1976-1980. Fewer frost days sounds pleasant, but water pipes, heat pumps and garden planting are all sized for a cold season that increasingly no longer arrives.
Is spring arriving earlier in Phoenix?
Spring now starts about 0.1 weeks earlier than in 1976-1980. The start point is the first day the trailing seven-day average high crosses 12°C, a fixed in-house measure used only to compare Phoenix against itself rather than against other cities.
Has the growing season in Phoenix grown longer?
The growing season here is measured as the stretch between the start of spring and the first autumn night below freezing. Phoenix has no reliable autumn frost in this record, so that measure yields no meaningful number.
Is rainfall in Phoenix getting heavier?
Phoenix averaged 3.6 days a year with more than 20mm of rain in 2021-2025, down from 4.2 in 1976-1980. This capital gets fewer heavy rain days now, which brings its own problems in a drying climate.
