Tiffin climate

Tiffin Frost Dates and Growing Season

NOAA 1991-2020 normals for Tiffin, 1 km from Tiffin, elevation 740 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tiffin. 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 23 and the first fall freeze around October 23, a growing season of about 184 days.

Median at 36°F
last May 2, first October 11
Median at 32°F
last April 23, first October 23
Median at 28°F
last April 11, first November 3

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 17May 12May 8May 5May 2Apr 29Apr 27Apr 23Apr 18
32°FMay 7May 2Apr 29Apr 26Apr 23Apr 20Apr 17Apr 13Apr 8
28°FApr 26Apr 21Apr 17Apr 14Apr 11Apr 8Apr 5Apr 1Mar 28
24°FApr 15Apr 9Apr 5Apr 2Mar 31Mar 29Mar 25Mar 20Mar 14
20°FApr 4Mar 31Mar 27Mar 23Mar 19Mar 16Mar 13Mar 8Mar 3
16°FMar 26Mar 20Mar 16Mar 13Mar 9Mar 6Mar 2Feb 27Feb 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°FSep 30Oct 3Oct 6Oct 9Oct 11Oct 14Oct 18Oct 20Oct 24
32°FOct 9Oct 14Oct 18Oct 21Oct 23Oct 26Oct 30Nov 1Nov 5
28°FOct 21Oct 27Oct 30Nov 1Nov 3Nov 5Nov 9Nov 13Nov 19
24°FNov 1Nov 5Nov 8Nov 12Nov 15Nov 18Nov 22Nov 27Dec 2
20°FNov 9Nov 15Nov 19Nov 23Nov 28Dec 1Dec 4Dec 8Dec 15
16°FNov 20Nov 27Dec 1Dec 4Dec 7Dec 11Dec 16Dec 21Dec 25

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°F181173169166162158154149142
32°F203196191187184180176170162
28°F228220215211207202198194186
24°F254245239234229225220216210
20°F275267261256251248243236228
16°F297288282277272267262257249

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
5,992
Cooling degree days, base 65°F
873
Growing degree days, base 40°F
5,399
Growing degree days, base 45°F
4,229
Growing degree days, base 50°F
3,194
Growing degree days, base 55°F
2,289
Growing degree days, base 60°F
1,514

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,20902
February1,02302
March849123
April4788113
May18660350
June33189606
July3274736
August7228687
September8398467
October37514171
November704034
December1,04305

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 1 km from Tiffin. 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 USC00338313 (Tiffin). Public domain.