When is the last frost in Ajo, AZ?

For ZIP code 85321, the average last spring frost (32°F) is January 10, based on NOAA 1991-2020 climate normals for the Ajo, AZ weather station. There is a 1-in-10 chance of a frost after February 15.

When is the first frost in Ajo, AZ?

The average first fall frost (32°F) is December 21. There is a 1-in-10 chance of frost by November 25, so tender plants are at risk from that point on.

How long is the growing season in 85321?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 347 days long.

Are these frost dates a forecast?

No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.

Frost dates for 85321Ajo, AZ

The average last spring frost in Ajo is January 10 and the average first fall frost is December 21, giving a typical growing season of about 347 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jan 10
Average first fall frost: Dec 21
Growing season: 347 days

Frost risk by date

NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.

Spring dates: chance of a frost AFTER the date. Fall dates: chance of a frost BEFORE the date.
Temperature	Last spring: 90% / 50% / 10% chance	First fall: 10% / 50% / 90% chance	Growing season (50%)	Years with at least one
Light frost (36°F)	Jan 3 · Feb 5 · Mar 13	Nov 19 · Dec 8 · Dec 30	306 days	99%
Frost / freeze (32°F)	Dec 11 · Jan 10 · Feb 15	Nov 25 · Dec 21 · Jan 24	347 days	81%
Hard freeze (28°F)	Nov 30 · Jan 8 · Feb 10	Nov 27 · Jan 3 · Feb 5	365 days	29%

Where these dates come from

ZIP code 85321 is matched to the NOAA station Ajo, AZ, 24.8 km away, at 1,751 ft elevation (286 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Ajo, AZ (used)	1,751 ft	Jan 10	Dec 21
Organ Pipe Cactus Nm, AZ	1,678 ft	Feb 4	Dec 15
Gila Bend 2Se, AZ	794 ft	Jan 23	Dec 11
Painted Rock Dam, AZ	568 ft	Jan 21	Dec 15

Frost dates near Ajo

Lukeville, AZ 85341 · last Feb 4, first Dec 15
Sells, AZ 85634 · last Mar 27, first Nov 9
Gila Bend, AZ 85337 · last Jan 23, first Dec 11
Topawa, AZ 85639 · last Mar 27, first Nov 9
Stanfield, AZ 85172 · last Feb 5, first Dec 6
Maricopa, AZ 85139 · last Feb 23, first Nov 24
Dateland, AZ 85333 · last Jan 25, first Dec 13
Casa Grande, AZ 85193 · last Feb 5, first Dec 6

Frequently asked questions

When is the last frost in Ajo, AZ?: For ZIP code 85321, the average last spring frost (32°F) is January 10, based on NOAA 1991-2020 climate normals for the Ajo, AZ weather station. There is a 1-in-10 chance of a frost after February 15.
When is the first frost in Ajo, AZ?: The average first fall frost (32°F) is December 21. There is a 1-in-10 chance of frost by November 25, so tender plants are at risk from that point on.
How long is the growing season in 85321?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 347 days long.
Are these frost dates a forecast?: No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.