Britton climate

Britton Frost Dates and Growing Season

NOAA 1991-2020 normals for Britton, 0.4 km from Britton, elevation 1355 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Britton. 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 13 and the first fall freeze around September 26, a growing season of about 135 days.

Median at 36°F
last May 23, first September 16
Median at 32°F
last May 13, first September 26
Median at 28°F
last May 2, first October 3

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 5May 31May 28May 25May 23May 20May 17May 13May 9
32°FMay 27May 22May 19May 15May 13May 10May 7May 3Apr 29
28°FMay 18May 13May 8May 5May 2Apr 30Apr 28Apr 23Apr 18
24°FMay 8May 2Apr 30Apr 26Apr 22Apr 19Apr 16Apr 12Apr 8
20°FApr 29Apr 22Apr 18Apr 15Apr 12Apr 10Apr 7Apr 4Apr 1
16°FApr 20Apr 14Apr 10Apr 7Apr 4Apr 2Mar 31Mar 27Mar 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 3Sep 8Sep 11Sep 14Sep 16Sep 19Sep 22Sep 24Sep 28
32°FSep 14Sep 18Sep 21Sep 24Sep 26Sep 28Sep 30Oct 3Oct 7
28°FSep 23Sep 26Sep 28Oct 1Oct 3Oct 5Oct 9Oct 12Oct 18
24°FSep 30Oct 3Oct 6Oct 9Oct 12Oct 15Oct 19Oct 23Oct 27
20°FOct 8Oct 13Oct 16Oct 20Oct 23Oct 27Oct 30Nov 2Nov 6
16°FOct 17Oct 23Oct 28Oct 31Nov 2Nov 4Nov 7Nov 11Nov 15

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°F13412812311911611310910497
32°F153147142139135132128123116
28°F173165161156153150146141135
24°F190183178175171167163158151
20°F210204199195190185181176170
16°F229221217213209205200195187

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
8,744
Cooling degree days, base 65°F
505
Growing degree days, base 40°F
4,162
Growing degree days, base 45°F
3,201
Growing degree days, base 50°F
2,347
Growing degree days, base 55°F
1,605
Growing degree days, base 60°F
984

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,69200
February1,40000
March1,14204
April675145
May31322225
June7498475
July22189632
August36146575
September20146315
October609374
November1,07103
December1,50800

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 0.4 km from Britton. 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 USC00391049 (Britton). Public domain.