Caribou climate

Caribou Frost Dates and Growing Season

NOAA 1991-2020 normals for Caribou Muni AP, 1.1 km from Caribou, elevation 624 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Caribou Muni AP. 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 7 and the first fall freeze around October 1, a growing season of about 143 days.

Median at 36°F
last May 24, first September 19
Median at 32°F
last May 7, first October 1
Median at 28°F
last April 26, first October 12

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 7Jun 2May 30May 27May 24May 21May 17May 13May 7
32°FMay 24May 17May 13May 10May 7May 5May 2Apr 30Apr 27
28°FMay 7May 3Apr 30Apr 29Apr 26Apr 24Apr 21Apr 19Apr 15
24°FApr 27Apr 23Apr 21Apr 19Apr 17Apr 14Apr 12Apr 9Apr 6
20°FApr 20Apr 17Apr 13Apr 11Apr 9Apr 7Apr 5Apr 3Mar 31
16°FApr 15Apr 10Apr 7Apr 5Apr 3Apr 2Mar 31Mar 28Mar 22

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 6Sep 10Sep 13Sep 17Sep 19Sep 22Sep 24Sep 28Oct 1
32°FSep 17Sep 22Sep 25Sep 28Oct 1Oct 2Oct 5Oct 7Oct 14
28°FSep 29Oct 2Oct 6Oct 9Oct 12Oct 16Oct 21Oct 25Oct 30
24°FOct 11Oct 17Oct 22Oct 27Oct 29Nov 1Nov 3Nov 6Nov 10
20°FOct 25Oct 31Nov 2Nov 5Nov 7Nov 10Nov 12Nov 17Nov 21
16°FNov 4Nov 8Nov 11Nov 14Nov 16Nov 19Nov 22Nov 25Nov 29

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°F13713012512111711311010599
32°F160155150147143140135130124
28°F188180175171167163160156151
24°F210204200196193189185181174
20°F229223219215211208204200195
16°F243237233229226223220216210

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
9,048
Cooling degree days, base 65°F
225
Growing degree days, base 40°F
3,418
Growing degree days, base 45°F
2,510
Growing degree days, base 50°F
1,726
Growing degree days, base 55°F
1,071
Growing degree days, base 60°F
561

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,65200
February1,42100
March1,24201
April79409
May4037131
June14839343
July4395518
August7168462
September26917221
October635138
November97404
December1,39800

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 1.1 km from Caribou. 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 USW00014607 (Caribou Muni AP). Public domain.