Hannibal climate

Hannibal Frost Dates and Growing Season

NOAA 1991-2020 normals for Hannibal Wtr Wks, 2.2 km from Hannibal, elevation 712 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hannibal Wtr Wks. 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 10 and the first fall freeze around October 27, a growing season of about 199 days.

Median at 36°F
last April 21, first October 18
Median at 32°F
last April 10, first October 27
Median at 28°F
last March 31, first November 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°FMay 6May 1Apr 28Apr 25Apr 21Apr 19Apr 15Apr 11Apr 6
32°FApr 25Apr 21Apr 17Apr 13Apr 10Apr 7Apr 4Apr 2Mar 28
28°FApr 15Apr 9Apr 6Apr 3Mar 31Mar 28Mar 25Mar 20Mar 14
24°FApr 6Mar 31Mar 29Mar 25Mar 21Mar 17Mar 13Mar 9Mar 3
20°FMar 30Mar 24Mar 20Mar 16Mar 12Mar 8Mar 5Mar 1Feb 24
16°FMar 21Mar 15Mar 12Mar 8Mar 5Mar 2Feb 27Feb 22Feb 14

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 2Oct 8Oct 12Oct 15Oct 18Oct 20Oct 23Oct 26Oct 30
32°FOct 14Oct 19Oct 22Oct 25Oct 27Oct 30Nov 1Nov 4Nov 9
28°FOct 23Oct 28Oct 31Nov 2Nov 5Nov 7Nov 11Nov 15Nov 21
24°FOct 31Nov 4Nov 7Nov 10Nov 14Nov 17Nov 21Nov 26Dec 1
20°FNov 7Nov 13Nov 17Nov 20Nov 24Nov 27Dec 1Dec 5Dec 12
16°FNov 16Nov 21Nov 26Nov 30Dec 2Dec 6Dec 10Dec 15Dec 20

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°F199191187182179174170166159
32°F217211207203199195191187180
28°F241233227223218214210205198
24°F265254248242238233228222215
20°F281273267261256252247241233
16°F298289283278273269263257249

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
5,515
Cooling degree days, base 65°F
1,181
Growing degree days, base 40°F
6,079
Growing degree days, base 45°F
4,847
Growing degree days, base 50°F
3,741
Growing degree days, base 55°F
2,761
Growing degree days, base 60°F
1,902

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,20102
February96307
March725353
April36816178
May12886428
June13247684
July1358821
August4307769
September67139524
October32423220
November677249
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 2.2 km from Hannibal. 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 USC00233601 (Hannibal Wtr Wks). Public domain.