Atchison County climate

Atchison County Frost Dates and Growing Season

NOAA 1991-2020 normals for Tarkio, 3.4 km from Atchison County, elevation 1045 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tarkio. 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 19 and the first fall freeze around October 15, a growing season of about 177 days.

Median at 36°F
last April 30, first October 5
Median at 32°F
last April 19, first October 15
Median at 28°F
last April 9, first October 25

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 13May 7May 4May 2Apr 30Apr 27Apr 24Apr 21Apr 16
32°FMay 4Apr 30Apr 26Apr 23Apr 19Apr 16Apr 13Apr 10Apr 6
28°FApr 25Apr 19Apr 15Apr 12Apr 9Apr 7Apr 4Apr 1Mar 25
24°FApr 16Apr 11Apr 7Apr 3Mar 31Mar 29Mar 24Mar 19Mar 12
20°FApr 7Mar 31Mar 28Mar 23Mar 19Mar 16Mar 12Mar 8Mar 3
16°FMar 29Mar 21Mar 16Mar 13Mar 10Mar 6Mar 4Mar 1Feb 23

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 23Sep 27Oct 1Oct 3Oct 5Oct 8Oct 11Oct 14Oct 17
32°FOct 1Oct 5Oct 9Oct 12Oct 15Oct 18Oct 20Oct 23Oct 27
28°FOct 11Oct 16Oct 19Oct 22Oct 25Oct 28Oct 29Nov 1Nov 7
24°FOct 20Oct 25Oct 29Oct 31Nov 2Nov 5Nov 9Nov 13Nov 19
20°FOct 29Nov 2Nov 6Nov 9Nov 13Nov 17Nov 21Nov 26Dec 2
16°FNov 6Nov 11Nov 17Nov 21Nov 25Nov 28Dec 2Dec 6Dec 13

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°F176171166162159155152147142
32°F195189185180177174169165157
28°F217210205201198194190184177
24°F241232226221217212208203197
20°F263255249244237233228222214
16°F282273268263258253247241232

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
6,051
Cooling degree days, base 65°F
1,009
Growing degree days, base 40°F
5,611
Growing degree days, base 45°F
4,443
Growing degree days, base 50°F
3,402
Growing degree days, base 55°F
2,477
Growing degree days, base 60°F
1,675

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26600
February1,03703
March758142
April4237140
May16459366
June16220654
July2321784
August6271730
September91112475
October39519179
November753029
December1,14101

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 3.4 km from Atchison County. 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 USW00014945 (Tarkio). Public domain.