Hillcrest climate

Hillcrest Frost Dates and Growing Season

NOAA 1991-2020 normals for Rochelle, 4.4 km from Hillcrest, elevation 775 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rochelle. 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 26 and the first fall freeze around October 13, a growing season of about 168 days.

Median at 36°F
last May 5, first October 3
Median at 32°F
last April 26, first October 13
Median at 28°F
last April 14, first October 24

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 21May 16May 12May 8May 5May 2Apr 30Apr 27Apr 22
32°FMay 12May 6May 2Apr 30Apr 26Apr 22Apr 20Apr 16Apr 11
28°FApr 30Apr 24Apr 21Apr 17Apr 14Apr 11Apr 8Apr 4Mar 31
24°FApr 18Apr 12Apr 8Apr 5Apr 3Apr 1Mar 29Mar 23Mar 18
20°FApr 6Apr 1Mar 30Mar 26Mar 22Mar 19Mar 16Mar 12Mar 7
16°FMar 29Mar 24Mar 20Mar 17Mar 14Mar 11Mar 8Mar 5Feb 28

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 19Sep 24Sep 28Sep 30Oct 3Oct 5Oct 8Oct 11Oct 15
32°FSep 29Oct 4Oct 8Oct 11Oct 13Oct 16Oct 19Oct 22Oct 25
28°FOct 11Oct 15Oct 19Oct 22Oct 24Oct 26Oct 29Nov 1Nov 5
24°FOct 22Oct 26Oct 29Nov 1Nov 3Nov 5Nov 9Nov 13Nov 17
20°FNov 1Nov 4Nov 8Nov 11Nov 14Nov 17Nov 20Nov 24Nov 28
16°FNov 7Nov 12Nov 16Nov 19Nov 22Nov 25Nov 29Dec 2Dec 7

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°F168161157152148144141135128
32°F188181177172168164159155147
28°F210204199195191186181178170
24°F233226221216212209205200193
20°F258251245240235231226222214
16°F276269263258254249244239232

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
6,875
Cooling degree days, base 65°F
692
Growing degree days, base 40°F
4,892
Growing degree days, base 45°F
3,799
Growing degree days, base 50°F
2,833
Growing degree days, base 55°F
1,988
Growing degree days, base 60°F
1,272

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,39200
February1,15301
March912119
April524381
May23146300
June39154566
July10221676
August17179628
September12778408
October4439136
November819017
December1,20902

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 4.4 km from Hillcrest. 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 USC00117354 (Rochelle). Public domain.