Greenbush climate

Greenbush Frost Dates and Growing Season

NOAA 1991-2020 normals for Agassiz Refuge, 46.9 km from Greenbush, elevation 1142 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Agassiz Refuge. 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 6 and the first fall freeze around October 3, a growing season of about 148 days.

Median at 36°F
last May 15, first September 24
Median at 32°F
last May 6, first October 3
Median at 28°F
last April 28, 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°FMay 30May 25May 22May 18May 15May 12May 9May 6May 3
32°FMay 20May 15May 11May 8May 6May 3May 1Apr 29Apr 25
28°FMay 11May 6May 3Apr 30Apr 28Apr 26Apr 23Apr 19Apr 14
24°FMay 3Apr 28Apr 25Apr 22Apr 19Apr 16Apr 13Apr 10Apr 6
20°FApr 26Apr 21Apr 17Apr 14Apr 11Apr 9Apr 6Apr 4Mar 31
16°FApr 19Apr 13Apr 9Apr 7Apr 5Apr 3Apr 1Mar 28Mar 21

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 10Sep 16Sep 19Sep 21Sep 24Sep 26Sep 29Oct 2Oct 6
32°FSep 20Sep 25Sep 28Oct 1Oct 3Oct 5Oct 8Oct 10Oct 16
28°FSep 30Oct 3Oct 6Oct 9Oct 12Oct 15Oct 18Oct 22Oct 26
24°FOct 8Oct 13Oct 16Oct 20Oct 23Oct 26Oct 29Nov 1Nov 4
20°FOct 16Oct 22Oct 26Oct 29Nov 1Nov 2Nov 5Nov 8Nov 12
16°FOct 26Oct 30Nov 1Nov 3Nov 6Nov 9Nov 12Nov 15Nov 20

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°F148143137133129125121116109
32°F166160155151148145141136128
28°F185178173169166162158154147
24°F204198193189185181177172164
20°F219214209205201198193188180
16°F232226222217214211207203197

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
9,275
Cooling degree days, base 65°F
470
Growing degree days, base 40°F
4,029
Growing degree days, base 45°F
3,103
Growing degree days, base 50°F
2,275
Growing degree days, base 55°F
1,548
Growing degree days, base 60°F
938

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,82000
February1,50400
March1,21801
April701139
May30922229
June7298478
July23167609
August37141569
September21339296
October644254
November1,12201
December1,61300

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 46.9 km from Greenbush. 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 USC00210050 (Agassiz Refuge). Public domain.