Prescott climate

Prescott Frost Dates and Growing Season

NOAA 1991-2020 normals for Prescott, 4.7 km from Prescott, elevation 5205 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Prescott. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around April 30 and the first fall freeze around October 20, a growing season of about 172 days.

Median at 36°F
last May 12, first October 10
Median at 32°F
last April 30, first October 20
Median at 28°F
last April 13, first October 31

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 30May 23May 18May 16May 12May 9May 6May 2Apr 28
32°FMay 15May 10May 6May 2Apr 30Apr 27Apr 23Apr 20Apr 14
28°FMay 2Apr 26Apr 21Apr 17Apr 13Apr 10Apr 7Apr 3Mar 28
24°FApr 16Apr 8Apr 3Mar 31Mar 26Mar 19Mar 15Mar 10Mar 5
20°FMar 30Mar 18Mar 13Mar 8Mar 4Feb 28Feb 24Feb 15Feb 6
16°FMar 7Mar 2Feb 24Feb 18Feb 10Feb 5Jan 31Jan 22Jan 11

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 29Oct 3Oct 5Oct 8Oct 10Oct 13Oct 16Oct 19Oct 23
32°FOct 7Oct 11Oct 15Oct 17Oct 20Oct 23Oct 26Oct 30Nov 4
28°FOct 16Oct 21Oct 24Oct 28Oct 31Nov 3Nov 7Nov 11Nov 15
24°FOct 24Nov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 21Nov 26
20°FNov 5Nov 13Nov 17Nov 20Nov 23Nov 26Nov 29Dec 3Dec 9
16°FNov 18Nov 24Nov 29Dec 2Dec 5Dec 9Dec 15Dec 20Dec 26

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F168162159154150147142137129
32°F193187182177172167164159153
28°F222214208204200195189184175
24°F255247241235230225220215206
20°F293283275269263257252245234
16°F332320311304297291283276266

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
4,388
Cooling degree days, base 65°F
916
Growing degree days, base 40°F
6,013
Growing degree days, base 45°F
4,611
Growing degree days, base 50°F
3,424
Growing degree days, base 55°F
2,424
Growing degree days, base 60°F
1,590

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January83101
February67805
March577042
April3741131
May17036340
June23182609
July1320784
August1263727
September39108519
October2717227
November579038
December84501

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 4.7 km from Prescott. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00026796 (Prescott). Public domain.