Portage climate

Portage Frost Dates and Growing Season

NOAA 1991-2020 normals for Portage Wwtp, 2.3 km from Portage, elevation 785 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Portage Wwtp. 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 10, a growing season of about 164 days.

Median at 36°F
last May 8, first September 30
Median at 32°F
last April 28, first October 10
Median at 28°F
last April 16, first October 22

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 14May 11May 8May 5May 2Apr 30Apr 26
32°FMay 12May 7May 3Apr 30Apr 28Apr 25Apr 22Apr 19Apr 14
28°FApr 30Apr 26Apr 22Apr 20Apr 16Apr 13Apr 10Apr 7Apr 4
24°FApr 20Apr 15Apr 11Apr 8Apr 6Apr 3Apr 1Mar 29Mar 23
20°FApr 11Apr 7Apr 3Mar 31Mar 30Mar 26Mar 22Mar 18Mar 13
16°FApr 3Mar 30Mar 27Mar 23Mar 20Mar 16Mar 14Mar 10Mar 7

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 17Sep 22Sep 25Sep 27Sep 30Oct 2Oct 4Oct 7Oct 11
32°FSep 26Oct 1Oct 3Oct 7Oct 10Oct 12Oct 14Oct 18Oct 23
28°FOct 6Oct 13Oct 16Oct 20Oct 22Oct 25Oct 27Oct 30Nov 4
24°FOct 21Oct 25Oct 29Nov 1Nov 2Nov 5Nov 8Nov 12Nov 17
20°FNov 1Nov 3Nov 7Nov 10Nov 13Nov 16Nov 20Nov 24Nov 29
16°FNov 7Nov 12Nov 16Nov 20Nov 23Nov 25Nov 28Dec 2Dec 8

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°F162156152148145141137132126
32°F184178173168164160156152145
28°F207201197192188183179174167
24°F230223218214210206202198191
20°F251244238233229225221216210
16°F268261256251246242238232225

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
7,342
Cooling degree days, base 65°F
622
Growing degree days, base 40°F
4,612
Growing degree days, base 45°F
3,565
Growing degree days, base 50°F
2,641
Growing degree days, base 55°F
1,838
Growing degree days, base 60°F
1,161

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,45700
February1,20700
March986113
April580365
May25437273
June50137537
July11216670
August23167609
September15958358
October4965102
November863013
December1,25701

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 2.3 km from Portage. 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 USC00476718 (Portage Wwtp). Public domain.