West Ishpeming climate

West Ishpeming Frost Dates and Growing Season

NOAA 1991-2020 normals for Ishpeming Wwtp, 1.2 km from West Ishpeming, elevation 1406 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ishpeming 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 May 26 and the first fall freeze around September 25, a growing season of about 119 days.

Median at 36°F
last June 5, first September 9
Median at 32°F
last May 26, first September 25
Median at 28°F
last May 12, first October 7

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 27Jun 18Jun 12Jun 9Jun 5Jun 3May 31May 28May 24
32°FJun 8Jun 3May 31May 28May 26May 22May 20May 15May 10
28°FMay 27May 22May 19May 15May 12May 9May 5May 2Apr 29
24°FMay 16May 10May 6May 3May 1Apr 29Apr 27Apr 23Apr 19
20°FMay 3Apr 30Apr 28Apr 25Apr 22Apr 19Apr 16Apr 12Apr 8
16°FApr 26Apr 22Apr 18Apr 15Apr 12Apr 9Apr 7Apr 4Mar 31

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 23Aug 30Sep 2Sep 5Sep 9Sep 12Sep 17Sep 21Sep 28
32°FSep 4Sep 12Sep 17Sep 21Sep 25Sep 28Oct 1Oct 5Oct 9
28°FSep 20Sep 26Oct 1Oct 4Oct 7Oct 9Oct 13Oct 17Oct 23
24°FOct 2Oct 9Oct 13Oct 17Oct 21Oct 25Oct 28Oct 31Nov 4
20°FOct 19Oct 26Oct 30Nov 1Nov 2Nov 4Nov 8Nov 12Nov 16
16°FNov 1Nov 3Nov 7Nov 10Nov 13Nov 15Nov 18Nov 21Nov 26

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°F116109103979388827767
32°F14113412912411911511010395
28°F166158153149146141137131122
24°F189182178174169165161155146
20°F213205200196193188184179173
16°F232224220216212208204200194

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
9,337
Cooling degree days, base 65°F
205
Growing degree days, base 40°F
3,218
Growing degree days, base 45°F
2,356
Growing degree days, base 50°F
1,612
Growing degree days, base 55°F
991
Growing degree days, base 60°F
516

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,57800
February1,39100
March1,27604
April864011
May4647124
June17339326
July7685474
August10454417
September29020214
October675140
November1,03801
December1,40900

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 West Ishpeming. 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 USC00204130 (Ishpeming Wwtp). Public domain.