Frost dates / Arizona / Flagstaff

Frost dates in Flagstaff, AZ

The station on this page is FLAGSTAFF PULLIAM AP, AZ US (USW00003103), 3.8 miles from the city point. Population in the Census 2024 estimate is 77,539.

Zone 6aUSDA average annual extreme minimum -10°F to -5°F, from ZIP 86005 (6.7 miles from the city point used on this page).

Median last 32°F is June 4. Median first 32°F is September 28. The 50% growing-season length is 115 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

Probability	Date	How to read it
90%	May 21	Earlier date. A last 32°F on or after this day is common.
50%	June 4	Median.
10%	June 19	Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

Probability	Date	How to read it
10%	September 16	Earlier date. A first 32°F on or before this day is uncommon.
50%	September 28	Median.
90%	October 9	Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this long	Days
10%	133
50%	115
90%	96

28°F threshold

	10%	50%	90%
Last, on or after	June 6	May 20	May 1
First, on or before	September 28	October 9	October 22
Season at least	162 days	139 days	117 days

36°F threshold

	10%	50%	90%
Last, on or after	July 1	June 16	June 3
First, on or before	September 6	September 19	September 28
Season at least	109 days	92 days	73 days

Station FLAGSTAFF PULLIAM AP, AZ US (USW00003103). Completeness flag S, 26 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 2134.5 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

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Flagstaff, AZ

Zone 6aAverage annual extreme minimum -10°F to -5°F

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Arizona. Nearest qualified station: FLAGSTAFF PULLIAM AP, AZ US (USW00003103), 3.8 miles. Median last 32°F June 4. Median first 32°F September 28. The 50% growing-season length is 115 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	June 19	June 4	May 21
First 32°F on or before	September 16	September 28	October 9

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

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Planting calendar

Frost dates for Arizona are above. Planting windows appear for states with a cited extension guide. The fall and seed tools use the numbers you enter and the station dates.

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