Roseau climate

Roseau Frost Dates and Growing Season

NOAA 1991-2020 normals for Warroad, 32.1 km from Roseau, elevation 1073 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Warroad. 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 16 and the first fall freeze around September 24, a growing season of about 129 days.

Median at 36°F
last May 27, first September 14
Median at 32°F
last May 16, first September 24
Median at 28°F
last May 7, 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 8Jun 3Jun 1May 29May 27May 24May 21May 19May 15
32°FMay 30May 26May 23May 20May 16May 14May 11May 8May 5
28°FMay 22May 16May 12May 9May 7May 5May 3May 1Apr 28
24°FMay 12May 7May 4May 2Apr 30Apr 27Apr 25Apr 21Apr 17
20°FMay 3Apr 30Apr 27Apr 24Apr 21Apr 19Apr 16Apr 13Apr 8
16°FApr 27Apr 22Apr 19Apr 16Apr 14Apr 11Apr 8Apr 5Apr 2

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°FAug 31Sep 4Sep 8Sep 11Sep 14Sep 17Sep 19Sep 22Sep 25
32°FSep 11Sep 16Sep 19Sep 21Sep 24Sep 26Sep 29Oct 1Oct 6
28°FSep 19Sep 24Sep 28Oct 1Oct 3Oct 5Oct 9Oct 12Oct 17
24°FSep 29Oct 4Oct 8Oct 11Oct 14Oct 17Oct 20Oct 25Oct 29
20°FOct 9Oct 16Oct 20Oct 23Oct 27Oct 30Nov 1Nov 5Nov 9
16°FOct 20Oct 27Oct 31Nov 1Nov 4Nov 7Nov 9Nov 13Nov 17

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°F126120115111108104999485
32°F147141136132129125121116109
28°F166160156151147143139135128
24°F186179175170166162157152146
20°F206200195191187183179173164
16°F223216211207204200196192186

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
10,503
Cooling degree days, base 65°F
204
Growing degree days, base 40°F
3,192
Growing degree days, base 45°F
2,353
Growing degree days, base 50°F
1,621
Growing degree days, base 55°F
1,004
Growing degree days, base 60°F
522

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,93400
February1,62200
March1,36301
April866013
May4467130
June15141346
July6285488
August9859427
September32112188
October749028
November1,19700
December1,69600

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 32.1 km from Roseau. 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 USC00218679 (Warroad). Public domain.