Continental climate

Continental Frost Dates and Growing Season

NOAA 1991-2020 normals for Defiance, 22.2 km from Continental, elevation 700 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Defiance. 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 April 22 and the first fall freeze around October 24, a growing season of about 183 days.

Median at 36°F
last May 2, first October 13
Median at 32°F
last April 22, first October 24
Median at 28°F
last April 10, first November 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°FMay 18May 12May 8May 5May 2Apr 30Apr 25Apr 23Apr 19
32°FMay 8May 3Apr 30Apr 26Apr 22Apr 20Apr 17Apr 14Apr 10
28°FApr 27Apr 20Apr 17Apr 13Apr 10Apr 7Apr 4Apr 1Mar 27
24°FApr 14Apr 9Apr 5Apr 2Mar 31Mar 28Mar 25Mar 20Mar 15
20°FApr 4Mar 31Mar 28Mar 24Mar 21Mar 17Mar 14Mar 10Mar 5
16°FMar 28Mar 22Mar 17Mar 13Mar 10Mar 7Mar 3Feb 28Feb 21

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°FOct 1Oct 5Oct 8Oct 11Oct 13Oct 16Oct 19Oct 22Oct 26
32°FOct 11Oct 16Oct 19Oct 21Oct 24Oct 27Oct 30Nov 1Nov 6
28°FOct 22Oct 28Oct 31Nov 1Nov 4Nov 7Nov 10Nov 14Nov 19
24°FNov 3Nov 7Nov 10Nov 13Nov 16Nov 19Nov 24Nov 28Dec 4
20°FNov 10Nov 15Nov 19Nov 22Nov 26Dec 1Dec 4Dec 9Dec 17
16°FNov 18Nov 24Nov 29Dec 1Dec 6Dec 11Dec 16Dec 21Dec 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°F181174169165161157153149142
32°F202197192187183179175170162
28°F226220214211207203199194187
24°F251243238234230226222218212
20°F275267261255250245240235228
16°F296287282277272267261256247

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
6,146
Cooling degree days, base 65°F
861
Growing degree days, base 40°F
5,320
Growing degree days, base 45°F
4,168
Growing degree days, base 50°F
3,148
Growing degree days, base 55°F
2,256
Growing degree days, base 60°F
1,495

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,23801
February1,04701
March866123
April4836104
May19657338
June30188608
July2278741
August8221679
September9096458
October38513165
November729027
December1,07103

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 22.2 km from Continental. 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 USC00332098 (Defiance). Public domain.