Athol climate

Athol Frost Dates and Growing Season

NOAA 1991-2020 normals for Bayview Model Basin, 11.6 km from Athol, elevation 2087 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bayview Model Basin. 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 22 and the first fall freeze around September 22, a growing season of about 122 days.

Median at 36°F
last June 7, first September 6
Median at 32°F
last May 22, first September 22
Median at 28°F
last May 4, first October 4

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°FJul 1Jun 21Jun 15Jun 10Jun 7Jun 4Jun 1May 29May 22
32°FJun 6May 31May 28May 25May 22May 18May 14May 10May 5
28°FMay 23May 16May 12May 8May 4Apr 30Apr 26Apr 21Apr 12
24°FMay 6Apr 28Apr 20Apr 13Apr 7Apr 2Mar 30Mar 25Mar 17
20°FApr 7Mar 30Mar 23Mar 18Mar 14Mar 10Mar 7Mar 3Feb 25
16°FMar 17Mar 11Mar 6Mar 3Feb 28Feb 25Feb 20Feb 15Feb 5

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 20Aug 28Sep 1Sep 3Sep 6Sep 10Sep 14Sep 18Sep 23
32°FSep 3Sep 10Sep 15Sep 19Sep 22Sep 26Sep 30Oct 3Oct 7
28°FSep 18Sep 25Sep 29Oct 2Oct 4Oct 7Oct 11Oct 16Oct 21
24°FOct 1Oct 6Oct 11Oct 16Oct 20Oct 25Oct 28Nov 2Nov 11
20°FOct 14Oct 22Oct 27Nov 1Nov 4Nov 9Nov 14Nov 20Nov 27
16°FOct 25Nov 1Nov 7Nov 13Nov 18Nov 23Nov 28Dec 4Dec 12

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°F11410598938984787160
32°F14613713212712211511010496
28°F181172165159154149144137129
24°F225215207201195189183171160
20°F263253244238231226219212202
16°F295283274267261254247240230

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
7,421
Cooling degree days, base 65°F
149
Growing degree days, base 40°F
3,220
Growing degree days, base 45°F
2,261
Growing degree days, base 50°F
1,479
Growing degree days, base 55°F
862
Growing degree days, base 60°F
417

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12700
February96200
March88400
April647012
May4192110
June22813242
July7270464
August8158442
September2906187
October662020
November91501
December1,13600

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 11.6 km from Athol. 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 USC00100667 (Bayview Model Basin). Public domain.