Roscommon climate

Roscommon Frost Dates and Growing Season

NOAA 1991-2020 normals for Houghton Lk Roscommon AP, 16.7 km from Roscommon, elevation 1151 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Houghton Lk Roscommon AP. 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 19 and the first fall freeze around September 23, a growing season of about 125 days.

Median at 36°F
last June 3, first September 8
Median at 32°F
last May 19, first September 23
Median at 28°F
last May 4, first October 5

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 30Jun 18Jun 11Jun 7Jun 3May 31May 28May 25May 20
32°FJun 3May 30May 27May 23May 19May 16May 11May 6Apr 30
28°FMay 24May 18May 13May 7May 4Apr 30Apr 26Apr 23Apr 17
24°FMay 9May 2Apr 29Apr 25Apr 22Apr 18Apr 15Apr 11Apr 6
20°FApr 23Apr 19Apr 15Apr 12Apr 9Apr 5Apr 3Apr 1Mar 28
16°FApr 15Apr 10Apr 6Apr 3Apr 2Mar 31Mar 28Mar 24Mar 19

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 27Sep 1Sep 5Sep 8Sep 11Sep 15Sep 19Sep 25
32°FSep 6Sep 13Sep 17Sep 20Sep 23Sep 26Sep 29Oct 3Oct 7
28°FSep 21Sep 26Sep 30Oct 2Oct 5Oct 8Oct 14Oct 19Oct 25
24°FOct 2Oct 8Oct 15Oct 19Oct 24Oct 28Nov 1Nov 3Nov 9
20°FOct 22Oct 29Nov 1Nov 4Nov 7Nov 11Nov 14Nov 19Nov 25
16°FNov 4Nov 10Nov 13Nov 18Nov 21Nov 24Nov 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°F1201121051009590837664
32°F150141135130125121115110100
28°F178169164159154149143137128
24°F207200194189184179173167158
20°F232224219214210206202196189
16°F257249242238233227223219211

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
7,898
Cooling degree days, base 65°F
337
Growing degree days, base 40°F
3,858
Growing degree days, base 45°F
2,881
Growing degree days, base 50°F
2,035
Growing degree days, base 55°F
1,317
Growing degree days, base 60°F
738

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,42100
February1,25200
March1,09307
April683134
May33820197
June10269418
July41126550
August6691490
September22728268
October567365
November88506
December1,22300

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 16.7 km from Roscommon. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00094814 (Houghton Lk Roscommon AP). Public domain.