Sister Bay climate

Sister Bay Frost Dates and Growing Season

NOAA 1991-2020 normals for Ephraim 1NE-Wwtp, 3.1 km from Sister Bay, elevation 733 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ephraim 1NE-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 14 and the first fall freeze around October 18, a growing season of about 155 days.

Median at 36°F
last May 26, first October 4
Median at 32°F
last May 14, first October 18
Median at 28°F
last May 1, 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°FJun 7Jun 3May 31May 29May 26May 23May 20May 17May 11
32°FMay 28May 23May 20May 18May 14May 11May 7May 3Apr 28
28°FMay 17May 12May 8May 4May 1Apr 28Apr 26Apr 23Apr 18
24°FMay 2Apr 27Apr 24Apr 21Apr 19Apr 16Apr 13Apr 10Apr 4
20°FApr 21Apr 16Apr 13Apr 10Apr 7Apr 4Apr 2Mar 31Mar 26
16°FApr 12Apr 7Apr 4Apr 2Mar 31Mar 28Mar 24Mar 21Mar 15

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 24Sep 28Oct 1Oct 4Oct 7Oct 10Oct 14Oct 20
32°FOct 1Oct 6Oct 10Oct 14Oct 18Oct 22Oct 26Oct 30Nov 3
28°FOct 15Oct 21Oct 25Oct 29Nov 1Nov 3Nov 5Nov 9Nov 14
24°FNov 1Nov 4Nov 7Nov 10Nov 13Nov 15Nov 18Nov 21Nov 25
20°FNov 8Nov 13Nov 17Nov 19Nov 22Nov 25Nov 28Dec 1Dec 6
16°FNov 18Nov 23Nov 26Nov 29Dec 1Dec 4Dec 8Dec 11Dec 18

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°F150143138133129125121115108
32°F177169163159155151147142134
28°F200194188183180176171165158
24°F226218213210205202198193187
20°F249241236232228224220215210
16°F269261256251247243239234227

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
7,725
Cooling degree days, base 65°F
347
Growing degree days, base 40°F
3,963
Growing degree days, base 45°F
2,966
Growing degree days, base 50°F
2,108
Growing degree days, base 55°F
1,375
Growing degree days, base 60°F
780

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,41500
February1,23300
March1,09004
April718016
May3726157
June10449396
July27142579
August36112541
September16638329
October503180
November84505
December1,21700

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 3.1 km from Sister Bay. 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 USC00472626 (Ephraim 1NE-Wwtp). Public domain.