Farmers Loop climate

Farmers Loop Frost Dates and Growing Season

NOAA 1991-2020 normals for Aurora, 6 km from Farmers Loop, elevation 443 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Aurora. 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 May 16 and the first fall freeze around September 6, a growing season of about 112 days.

Median at 36°F
last May 27, first August 27
Median at 32°F
last May 16, first September 6
Median at 28°F
last May 7, first September 18

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°FJun 8Jun 3Jun 1May 29May 27May 25May 21May 18May 14
32°FMay 29May 25May 21May 18May 16May 13May 12May 9May 5
28°FMay 19May 14May 11May 9May 7May 4May 3Apr 30Apr 26
24°FMay 11May 7May 4May 2Apr 30Apr 27Apr 24Apr 21Apr 16
20°FMay 5May 1Apr 28Apr 25Apr 23Apr 20Apr 17Apr 14Apr 10
16°FApr 30Apr 26Apr 22Apr 19Apr 16Apr 14Apr 11Apr 9Apr 6

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°FAug 13Aug 18Aug 22Aug 24Aug 27Aug 30Sep 1Sep 4Sep 8
32°FAug 25Aug 30Sep 1Sep 3Sep 6Sep 9Sep 12Sep 16Sep 20
28°FSep 4Sep 9Sep 12Sep 15Sep 18Sep 21Sep 24Sep 26Sep 30
24°FSep 14Sep 19Sep 23Sep 25Sep 27Sep 29Oct 1Oct 5Oct 8
20°FSep 23Sep 27Sep 30Oct 2Oct 4Oct 6Oct 9Oct 12Oct 16
16°FSep 29Oct 2Oct 6Oct 8Oct 11Oct 13Oct 16Oct 19Oct 23

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°F10810298949187847872
32°F13012512011511210910510092
28°F150144140136133129125121115
24°F167162157153150147143139133
20°F182176171168164161157153148
16°F192187183180176173170165159

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
13,314
Cooling degree days, base 65°F
49
Growing degree days, base 40°F
2,368
Growing degree days, base 45°F
1,634
Growing degree days, base 50°F
1,010
Growing degree days, base 55°F
525
Growing degree days, base 60°F
204

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January2,24400
February1,75700
March1,61000
April92704
May463188
June16121314
July10923380
August2794200
September600024
October1,21101
November1,81800
December2,13800

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 6 km from Farmers Loop. 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 USC00500490 (Aurora). Public domain.