Island Falls climate

Island Falls Frost Dates and Growing Season

NOAA 1991-2020 normals for Patten 2, 17.6 km from Island Falls, elevation 820 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Patten 2. 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 30, a growing season of about 138 days.

Median at 36°F
last May 27, first September 20
Median at 32°F
last May 13, first September 30
Median at 28°F
last May 1, first October 10

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

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°F13312612111711411110710396
32°F157150145142138134130124117
28°F181174169165162158154149143
24°F206200195191187183179174167
20°F226221216212209206201197190
16°F243237233229226223219214208

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
9,033
Cooling degree days, base 65°F
180
Growing degree days, base 40°F
3,278
Growing degree days, base 45°F
2,384
Growing degree days, base 50°F
1,613
Growing degree days, base 55°F
973
Growing degree days, base 60°F
485

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,62100
February1,38200
March1,23800
April80409
May4324113
June16528318
July5575485
August7959445
September27613211
October647131
November96802
December1,36700

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 17.6 km from Island Falls. 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 USC00176594 (Patten 2). Public domain.