Two Harbors climate

Two Harbors Frost Dates and Growing Season

NOAA 1991-2020 normals for Two Harbors, 0.5 km from Two Harbors, elevation 625 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Two Harbors. 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 12 and the first fall freeze around October 6, a growing season of about 145 days.

Median at 36°F
last May 28, first September 27
Median at 32°F
last May 12, first October 6
Median at 28°F
last April 29, first October 20

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

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

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°F139132128124120116112108101
32°F167159153149145140136130122
28°F196189183178174170165160151
24°F218212207204200196192187180
20°F237230225221217214210206201
16°F254246241237233229225219214

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
8,778
Cooling degree days, base 65°F
161
Growing degree days, base 40°F
3,169
Growing degree days, base 45°F
2,253
Growing degree days, base 50°F
1,492
Growing degree days, base 55°F
888
Growing degree days, base 60°F
441

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,53300
February1,28900
March1,12500
April77608
May516056
June2699204
July7972459
August6067473
September22812248
October592044
November95901
December1,35300

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 0.5 km from Two Harbors. 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 USC00218419 (Two Harbors). Public domain.