About 0.5°F per decade, measured from Tempe's official daily weather records, 1971–2025. Individual years still bounce around — some recent ones came in cool — but the long-term line has clearly risen.
Is that a lot? Tempe's warming is broadly in line with other cities in United States — neither unusually fast nor unusually slow.
What has actually changed
Each card compares the 1970s (the first ten years of the
record) with recent years (the last ten) — the same span
the headline and the chart use.
Freezing nights
7 fewer nights
1970s
20 / yr
→
Recent
13 / yr
Milder winters — fewer frosts
Average temperature
+1.3°F
1970s
70.9°F
→
Recent
72.1°F
A steady upward drift
Hot days above 90°F
14 fewer days
1970s
174 / yr
→
Recent
160 / yr
Slightly fewer hot days
Rainy days
4 fewer days
1970s
38 / yr
→
Recent
34 / yr
Drier on average
Tempe's temperature, year by year
Average temperature for each year from 1971 to 2025.
a warmer-than-average year a cooler-than-average year
Each bar is one year. Most recent years sit above the older ones.
Some recent years still came in cool — warming is a slope,
not a straight climb.
In day-to-day terms, that long-term shift shows up as about 5 fewer freezing nights a year compared with the 1970s.
When in the year the change shows up
How much warmer each month is now than in the 1970s.
Useful if you garden or care about a particular season —
otherwise the headline above already has the answer.
November has warmed the most — about 1.5°F. The warming runs across the whole year, not just one season.
Methodology & sources
Temperature — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Tempe Asu (NOAA GHCN station USC00028499), about 2 km from the city centre.