Crestline climate

Crestline Frost Dates and Growing Season

NOAA 1991-2020 normals for Lake Arrowhead, 9 km from Crestline, elevation 5205 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lake Arrowhead. 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 5 and the first fall freeze around November 2, a growing season of about 176 days.

Median at 36°F
last May 27, first October 18
Median at 32°F
last May 5, first November 2
Median at 28°F
last April 11, first November 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°FJun 10Jun 4Jun 2May 31May 27May 23May 18May 12May 3
32°FMay 31May 25May 18May 11May 5Apr 30Apr 26Apr 19Apr 9
28°FMay 12May 1Apr 24Apr 17Apr 11Apr 6Mar 31Mar 24Mar 14
24°FApr 10Apr 3Mar 29Mar 21Mar 16Mar 9Mar 2Feb 25Feb 10
20°FMar 23Mar 10Feb 28Feb 22Feb 11Feb 2Jan 25Jan 13Dec 31
16°FFeb 28Feb 12Feb 1Jan 21Jan 12Jan 6Jan 1Dec 25Dec 14

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 30Oct 5Oct 10Oct 13Oct 18Oct 23Oct 28Nov 1Nov 5
32°FOct 12Oct 19Oct 25Oct 30Nov 2Nov 5Nov 8Nov 11Nov 15
28°FOct 31Nov 5Nov 10Nov 13Nov 16Nov 19Nov 22Nov 25Nov 30
24°FNov 13Nov 20Nov 24Nov 27Dec 1Dec 4Dec 8Dec 13Dec 21
20°FNov 27Dec 3Dec 9Dec 14Dec 20Dec 25Dec 30Jan 9Jan 25
16°FDec 6Dec 14Dec 22Dec 28Jan 1Jan 8Jan 15Jan 29Feb 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°F170162156151145139134127117
32°F206196189182176170164157148
28°F249239230222215207200191180
24°F297283274266258251244236227
20°F353341332321310301290278265
16°F365365365365363355348337319

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
95% of years
16°F or colder
54% 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
5,433
Cooling degree days, base 65°F
401
Growing degree days, base 40°F
4,626
Growing degree days, base 45°F
3,389
Growing degree days, base 50°F
2,367
Growing degree days, base 55°F
1,540
Growing degree days, base 60°F
890

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January88200
February77401
March71909
April509058
May3506171
June11951388
July18145592
August15153603
September10344394
October3761138
November671013
December89700

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 9 km from Crestline. 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 USC00044671 (Lake Arrowhead). Public domain.