Portage climate

Portage Frost Dates and Growing Season

NOAA 1991-2020 normals for Kalamazoo Battle Ck Intl AP, 4.4 km from Portage, elevation 868 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Kalamazoo Battle Ck Intl AP. 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 April 28 and the first fall freeze around October 18, a growing season of about 172 days.

Median at 36°F
last May 8, first October 6
Median at 32°F
last April 28, first October 18
Median at 28°F
last April 17, first November 1

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 24May 18May 15May 11May 8May 5May 2Apr 29Apr 24
32°FMay 13May 8May 4May 1Apr 28Apr 25Apr 22Apr 18Apr 13
28°FMay 3Apr 28Apr 23Apr 20Apr 17Apr 14Apr 10Apr 7Apr 3
24°FApr 20Apr 15Apr 10Apr 7Apr 5Apr 3Mar 31Mar 28Mar 23
20°FApr 9Apr 4Apr 1Mar 30Mar 27Mar 24Mar 20Mar 18Mar 13
16°FMar 31Mar 28Mar 24Mar 21Mar 18Mar 15Mar 13Mar 9Mar 3

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 22Sep 27Sep 30Oct 3Oct 6Oct 9Oct 11Oct 14Oct 19
32°FOct 2Oct 8Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Nov 1
28°FOct 16Oct 22Oct 26Oct 30Nov 1Nov 3Nov 5Nov 8Nov 14
24°FNov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 19Nov 23Nov 30
20°FNov 8Nov 14Nov 17Nov 21Nov 24Nov 28Dec 1Dec 5Dec 11
16°FNov 20Nov 26Nov 30Dec 3Dec 6Dec 9Dec 14Dec 19Dec 25

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°F169162157153149145141136128
32°F192186181177172168163157150
28°F217210205201196192188182174
24°F241234228224220216212207200
20°F266258253247242238233228221
16°F288279275269265258253247238

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
6,326
Cooling degree days, base 65°F
710
Growing degree days, base 40°F
5,027
Growing degree days, base 45°F
3,894
Growing degree days, base 50°F
2,897
Growing degree days, base 55°F
2,032
Growing degree days, base 60°F
1,301

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,24601
February1,06101
March882124
April499494
May21544311
June39153564
July7241699
August12190643
September12069403
October4248133
November749021
December1,07403

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 4.4 km from Portage. 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 USW00094815 (Kalamazoo Battle Ck Intl AP). Public domain.