Stanford climate

Stanford Frost Dates and Growing Season

NOAA 1991-2020 normals for Stanford, 0.5 km from Stanford, elevation 4860 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Stanford. 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 May 25 and the first fall freeze around September 21, a growing season of about 118 days.

Median at 36°F
last June 12, first September 9
Median at 32°F
last May 25, first September 21
Median at 28°F
last May 10, first October 1

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°FJul 7Jun 28Jun 21Jun 16Jun 12Jun 8Jun 4May 31May 26
32°FJun 15Jun 6May 31May 28May 25May 22May 19May 15May 10
28°FMay 25May 19May 15May 12May 10May 7May 4May 1Apr 27
24°FMay 11May 6May 3Apr 30Apr 28Apr 26Apr 22Apr 17Apr 11
20°FMay 3Apr 28Apr 24Apr 20Apr 16Apr 13Apr 9Apr 4Mar 31
16°FApr 25Apr 19Apr 13Apr 10Apr 6Apr 3Mar 31Mar 26Mar 18

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°FAug 22Aug 29Sep 2Sep 5Sep 9Sep 12Sep 16Sep 20Sep 23
32°FSep 6Sep 11Sep 15Sep 18Sep 21Sep 24Sep 26Sep 29Oct 3
28°FSep 17Sep 23Sep 26Sep 29Oct 1Oct 3Oct 6Oct 10Oct 15
24°FSep 25Sep 30Oct 3Oct 5Oct 9Oct 12Oct 15Oct 19Oct 25
20°FOct 1Oct 6Oct 10Oct 14Oct 18Oct 22Oct 25Oct 30Nov 5
16°FOct 7Oct 14Oct 18Oct 23Oct 27Oct 31Nov 3Nov 7Nov 13

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°F11010297918681746758
32°F13713212712211811410810291
28°F160155151147143140136131123
24°F186178173168164160155150143
20°F209201194189184179173168160
16°F228220213207203197191184175

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
7,671
Cooling degree days, base 65°F
278
Growing degree days, base 40°F
3,641
Growing degree days, base 45°F
2,616
Growing degree days, base 50°F
1,777
Growing degree days, base 55°F
1,109
Growing degree days, base 60°F
611

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18601
February1,06202
March95007
April690025
May4492112
June21319266
July58118526
August70110508
September25826250
October621268
November929012
December1,18601

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 0.5 km from Stanford. 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 USC00247864 (Stanford). Public domain.