River Falls climate

River Falls Frost Dates and Growing Season

NOAA 1991-2020 normals for River Falls, 1.2 km from River Falls, elevation 940 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for River Falls. 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 11 and the first fall freeze around October 1, a growing season of about 143 days.

Median at 36°F
last May 23, first September 24
Median at 32°F
last May 11, first October 1
Median at 28°F
last May 1, first October 11

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

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

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°F143136131126123119114109102
32°F162156151146143139134129122
28°F183176171167162158153148142
24°F206199194190185181176171162
20°F225218213208205200196191184
16°F243235231226222217213209202

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
8,281
Cooling degree days, base 65°F
459
Growing degree days, base 40°F
4,154
Growing degree days, base 45°F
3,172
Growing degree days, base 50°F
2,305
Growing degree days, base 55°F
1,558
Growing degree days, base 60°F
935

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,60700
February1,33400
March1,09009
April650246
May31722214
June7891464
July19171617
August38122549
September19046322
October572479
November98107
December1,40600

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 1.2 km from River Falls. 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 USC00477226 (River Falls). Public domain.