Saint Ignace climate

Saint Ignace Frost Dates and Growing Season

NOAA 1991-2020 normals for St Ignace, 0.8 km from Saint Ignace, elevation 661 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for St Ignace. 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 16 and the first fall freeze around October 13, a growing season of about 149 days.

Median at 36°F
last May 28, first October 1
Median at 32°F
last May 16, first October 13
Median at 28°F
last May 4, first October 28

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 8Jun 4Jun 1May 31May 28May 25May 22May 19May 13
32°FMay 29May 25May 22May 19May 16May 13May 9May 6Apr 30
28°FMay 20May 15May 11May 7May 4May 1Apr 29Apr 24Apr 19
24°FMay 7May 1Apr 28Apr 24Apr 21Apr 19Apr 15Apr 12Apr 7
20°FApr 22Apr 19Apr 16Apr 12Apr 9Apr 7Apr 4Apr 1Mar 28
16°FApr 13Apr 9Apr 6Apr 3Apr 1Mar 30Mar 26Mar 22Mar 18

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 18Sep 22Sep 26Sep 29Oct 1Oct 4Oct 6Oct 10Oct 14
32°FSep 30Oct 4Oct 7Oct 10Oct 13Oct 17Oct 20Oct 24Oct 30
28°FOct 11Oct 17Oct 21Oct 25Oct 28Oct 31Nov 2Nov 5Nov 11
24°FOct 26Oct 31Nov 2Nov 5Nov 8Nov 12Nov 15Nov 20Nov 26
20°FNov 5Nov 9Nov 13Nov 17Nov 20Nov 24Nov 27Nov 30Dec 5
16°FNov 12Nov 18Nov 23Nov 27Nov 30Dec 2Dec 6Dec 11Dec 17

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°F144138133129126122119114107
32°F170163158154149145141136130
28°F198190185181177172167160153
24°F223215210206202198193188180
20°F247239234229224220215212206
16°F265260254249245240235228221

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
8,370
Cooling degree days, base 65°F
186
Growing degree days, base 40°F
3,431
Growing degree days, base 45°F
2,503
Growing degree days, base 50°F
1,710
Growing degree days, base 55°F
1,048
Growing degree days, base 60°F
529

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46100
February1,31700
March1,19200
April80703
May483177
June15317317
July4080505
August5166480
September21222269
October557155
November88204
December1,21500

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 0.8 km from Saint Ignace. 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 USC00207275 (St Ignace). Public domain.