Frost dates / Arizona / Maricopa

Frost dates in Maricopa, AZ

The station on this page is MARICOPA 4 N, AZ US (USC00025270), 5.3 miles from the city point. Population in the Census 2024 estimate is 76,654.

Zone 9aUSDA average annual extreme minimum 20°F to 25°F, from ZIP 85138 (1.7 miles from the city point used on this page).

Median last 32°F is February 23. Median first 32°F is November 24. The 50% growing-season length is 274 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%	January 29	Earlier date. A last 32°F on or after this day is common.
50%	February 23	Median.
10%	March 15	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%	November 10	Earlier date. A first 32°F on or before this day is uncommon.
50%	November 24	Median.
90%	December 8	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%	304
50%	274
90%	245

28°F threshold

	10%	50%	90%
Last, on or after	February 28	February 2	December 31
First, on or before	November 21	December 6	December 23
Season at least	344 days	310 days	278 days

36°F threshold

	10%	50%	90%
Last, on or after	April 10	March 12	February 24
First, on or before	October 27	November 14	November 28
Season at least	267 days	243 days	215 days

Station MARICOPA 4 N, AZ US (USC00025270). Completeness flag R, 22 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 353.6 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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Maricopa, AZ

Zone 9aAverage annual extreme minimum 20°F to 25°F

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

Arizona. Nearest qualified station: MARICOPA 4 N, AZ US (USC00025270), 5.3 miles. Median last 32°F February 23. Median first 32°F November 24. The 50% growing-season length is 274 days.

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32°F probabilities at this station

	10%	50%	90%
Last 32°F on or after	March 15	February 23	January 29
First 32°F on or before	November 10	November 24	December 8

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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