Chapman climate

Chapman Frost Dates and Growing Season

NOAA 1991-2020 normals for Chapman, 1.2 km from Chapman, elevation 1111 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chapman. 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 17 and the first fall freeze around October 20, a growing season of about 184 days.

Median at 36°F
last April 28, first October 10
Median at 32°F
last April 17, first October 20
Median at 28°F
last April 7, first October 30

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 9May 6May 2Apr 30Apr 28Apr 25Apr 22Apr 19Apr 14
32°FApr 30Apr 26Apr 23Apr 20Apr 17Apr 15Apr 12Apr 7Apr 2
28°FApr 21Apr 18Apr 14Apr 11Apr 7Apr 4Apr 1Mar 28Mar 22
24°FApr 14Apr 8Apr 4Apr 1Mar 29Mar 26Mar 22Mar 16Mar 10
20°FApr 3Mar 30Mar 26Mar 22Mar 17Mar 14Mar 10Mar 6Mar 1
16°FMar 24Mar 17Mar 14Mar 10Mar 7Mar 4Mar 1Feb 25Feb 20

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 26Sep 30Oct 4Oct 7Oct 10Oct 13Oct 15Oct 18Oct 22
32°FOct 3Oct 10Oct 14Oct 17Oct 20Oct 22Oct 25Oct 29Nov 2
28°FOct 16Oct 20Oct 24Oct 27Oct 30Nov 2Nov 5Nov 9Nov 13
24°FOct 26Oct 30Nov 2Nov 5Nov 8Nov 11Nov 15Nov 20Nov 25
20°FNov 1Nov 6Nov 10Nov 13Nov 17Nov 21Nov 25Nov 29Dec 4
16°FNov 9Nov 15Nov 19Nov 23Nov 27Dec 1Dec 4Dec 10Dec 16

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°F184178174170165161157152145
32°F204198193189184180176170163
28°F226219214209205201196191184
24°F248239233228224219215209203
20°F268261255250244239234227219
16°F290281275269264260254247239

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
5,220
Cooling degree days, base 65°F
1,415
Growing degree days, base 40°F
6,423
Growing degree days, base 45°F
5,163
Growing degree days, base 50°F
4,034
Growing degree days, base 55°F
3,034
Growing degree days, base 60°F
2,160

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13600
February88509
March667363
April33917198
May122110460
June6296741
July1416880
August2369832
September65174560
October30029247
November660142
December1,03801

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 1.2 km from Chapman. 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 USC00141435 (Chapman). Public domain.