Frost dates for Flagstaff
The typical last spring frost in Flagstaff is Jun 4, and the typical first fall frost is Sep 28. These dates come from Flagstaff Airport, and the growing season between them is 115 days.
NCEI U.S. Climate Normals 1991-2020, annual/seasonal (c20230404), USW00003103
This season's measured frost
No freeze has been recorded yet this fall at Flagstaff Airport; the lowest reading since July 1 is 34F on Jul 1, against a typical first frost date of Sep 28.
In 2026, the last spring freeze at Flagstaff Airport was on May 30 with a low of 28F, 5 days earlier than the typical date of Jun 4.
Readings come from official daily lows in the daily climate report of the National Weather Service, via the Iowa Environmental Mesonet.
Early, typical and late years for Flagstaff
| Year type | Last spring frost | First fall frost |
|---|---|---|
| Early year (1 in 10) | May 21 | Sep 16 |
| Typical year | Jun 4 | Sep 28 |
| Late year (1 in 10) | Jun 19 | Oct 9 |
For spring, an early year means 1 year in 10 has a last freeze before the early date, and a late year means 1 year in 10 has a last freeze after the late date. For fall, an early year means 1 year in 10 has a first freeze by the early date, and a late year means it holds off past the late date.
The growing season in a typical year is 115 days, with the shortest at 96 days and the longest at 133 days in 1 year in 10.
Frost and freeze thresholds
| Last spring frost | First fall frost | |
|---|---|---|
| Light frost (36F) | Jun 16 | Sep 19 |
| Freeze (32F) | Jun 4 | Sep 28 |
| Hard freeze (28F) | May 20 | Oct 9 |
Clear, calm nights can see frost on plants at a low of 36F. A low of 32F is a freeze, and most tender plants are killed at 28F, a hard freeze.
More weather for Flagstaff
A typical date is the median: half of years have an earlier last spring frost, half a later one. An early year means 1 year in 10, and a late year means 1 year in 10. Dates come from the U.S. Climate Normals for 1991-2020, published by NOAA's National Centers for Environmental Information, using a daily low of 32F or below as a freeze.
The daily climate report is issued by the local National Weather Service forecast office and delivered to this page by the Iowa Environmental Mesonet of Iowa State University. Under 17 U.S.C. 105, no copyright attaches to the government-produced figures on this page, including reports, alerts, station observations, and normals, which were created by the National Weather Service and other NOAA offices. The notice that 17 U.S.C. 403 requires appears in this sentence. It does not imply endorsement by or affiliation with those agencies. See: Data sources and attribution.