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Frost Dates in Arizona
First and last frost dates across Arizona, computed from 97 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
Apr 9
statewide median · range Jan 4–Jun 23
First fall frost
Nov 6
statewide median · range Sep 15–Jan 9
Growing season
211 days
median · range 81–365
Stations used
97
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Phoenix | Phoenix Ap · 4 mi | Jan 5 (cautious: Jan 22) | Jan 3 | 365 days | Jan 19 |
| Tucson | Tucson Intl Ap · 6 mi | Feb 5 (cautious: Mar 2) | Dec 9 | 307 days | Feb 19 |
| Mesa | Phoenix Ap · 10 mi | Jan 5 (cautious: Jan 22) | Jan 3 | 365 days | Jan 19 |
How frost varies across Arizona
Spring frost timing spans about 170 days across the state. Bullhead City in northwestern Arizona typically sees its last spring frost around January 4, while Flagstaff in northern Arizona doesn't clear frost until about June 23. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Arizona
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around April 23 for the statewide median. Check your city's row above rather than the statewide median: a 170-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 97 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
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Frequently asked questions
When is the last frost date in Arizona?
The statewide median last spring frost is April 9, but it ranges from January 4 to June 23 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Arizona?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around April 23 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Arizona?
The median growing season across 97 NOAA stations is 211 days, ranging from 81 to 365 days by location.
Why do frost dates vary so much within Arizona?
Frost timing follows latitude, elevation, and local terrain. Across Arizona, last spring frost dates span about 170 days — from around January 4 near Bullhead City to June 23 near Flagstaff. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.