Colton climate

Colton Frost Dates and Growing Season

NOAA 1991-2020 normals for Wentworth 2.5 Wnw, 25.5 km from Colton, elevation 1722 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wentworth 2.5 Wnw. 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 2 and the first fall freeze around October 5, a growing season of about 156 days.

Median at 36°F
last May 11, first September 27
Median at 32°F
last May 2, first October 5
Median at 28°F
last April 22, first October 16

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 23May 19May 16May 13May 11May 8May 6May 3Apr 30
32°FMay 14May 10May 7May 4May 2Apr 30Apr 27Apr 23Apr 18
28°FMay 6May 1Apr 28Apr 25Apr 22Apr 20Apr 17Apr 13Apr 9
24°FApr 26Apr 22Apr 18Apr 16Apr 12Apr 9Apr 7Apr 4Mar 31
20°FApr 19Apr 14Apr 9Apr 6Apr 4Apr 1Mar 30Mar 24Mar 18
16°FApr 11Apr 6Apr 2Mar 31Mar 28Mar 23Mar 20Mar 15Mar 10

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 15Sep 19Sep 22Sep 25Sep 27Sep 30Oct 2Oct 5Oct 10
32°FSep 24Sep 28Oct 1Oct 3Oct 5Oct 8Oct 12Oct 15Oct 19
28°FOct 1Oct 5Oct 9Oct 13Oct 16Oct 19Oct 22Oct 25Oct 30
24°FOct 12Oct 17Oct 20Oct 24Oct 26Oct 28Oct 31Nov 4Nov 9
20°FOct 21Oct 27Oct 30Nov 1Nov 4Nov 6Nov 9Nov 12Nov 18
16°FOct 30Nov 2Nov 6Nov 8Nov 11Nov 14Nov 18Nov 21Nov 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°F156150146142139135132127121
32°F174168164159156152149145139
28°F196189184179176172167162156
24°F217210204200197193188183175
20°F235228223218214210205200193
16°F251244238234229226221216209

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
7,586
Cooling degree days, base 65°F
661
Growing degree days, base 40°F
4,700
Growing degree days, base 45°F
3,652
Growing degree days, base 50°F
2,721
Growing degree days, base 55°F
1,905
Growing degree days, base 60°F
1,214

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,51900
February1,23600
March99408
April572371
May24435281
June44143549
July9237693
August20175620
September13964382
October5095104
November937012
December1,36400

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 25.5 km from Colton. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00399042 (Wentworth 2.5 Wnw). Public domain.