Whatcom County climate

Whatcom County Frost Dates and Growing Season

NOAA 1991-2020 normals for Upper Baker Dam, 23.7 km from Whatcom County, elevation 690 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Upper Baker Dam. 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 24 and the first fall freeze around October 29, a growing season of about 190 days.

Median at 36°F
last May 11, first October 14
Median at 32°F
last April 24, first October 29
Median at 28°F
last March 28, first November 17

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 28May 21May 17May 14May 11May 7May 4Apr 30Apr 26
32°FMay 9May 4Apr 30Apr 27Apr 24Apr 19Apr 15Apr 11Apr 4
28°FApr 17Apr 10Apr 5Mar 31Mar 28Mar 23Mar 17Mar 12Mar 5
24°FMar 25Mar 17Mar 10Mar 5Mar 1Feb 25Feb 18Feb 9Jan 29
20°FMar 8Feb 28Feb 21Feb 15Feb 6Jan 31Jan 19Jan 7Dec 27
16°FFeb 22Feb 12Feb 1Jan 26Jan 16Jan 6Dec 31Dec 18Dec 7

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 28Oct 3Oct 6Oct 10Oct 14Oct 17Oct 20Oct 24Oct 29
32°FOct 12Oct 18Oct 22Oct 25Oct 29Nov 1Nov 5Nov 10Nov 17
28°FOct 23Nov 1Nov 7Nov 11Nov 17Nov 21Nov 26Dec 1Dec 6
24°FNov 12Nov 21Nov 27Dec 1Dec 5Dec 10Dec 16Dec 24Jan 1
20°FNov 26Dec 2Dec 7Dec 14Dec 19Dec 27Jan 1Jan 9Jan 31
16°FDec 1Dec 6Dec 13Dec 20Dec 29Jan 2Jan 10Jan 23Feb 6

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°F178169163159154150145140132
32°F213205199195190184179173165
28°F266254245239234226220212201
24°F320304295287280274266258247
20°F362346334328320312304294279
16°F365365365362351343334324311

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
92% of years
16°F or colder
66% 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
6,468
Cooling degree days, base 65°F
87
Growing degree days, base 40°F
3,445
Growing degree days, base 45°F
2,351
Growing degree days, base 50°F
1,470
Growing degree days, base 55°F
795
Growing degree days, base 60°F
331

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January98000
February81900
March78002
April576028
May3802126
June2428221
July10835392
August8936412
September2197243
October522045
November78000
December97500

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 23.7 km from Whatcom County. 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 USC00458715 (Upper Baker Dam). Public domain.