Aurora climate

Aurora Frost Dates and Growing Season

NOAA 1991-2020 normals for Aurora 6 N, 9.1 km from Aurora, elevation 20 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Aurora 6 N. 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 March 8 and the first fall freeze around December 5, a growing season of about 272 days.

Median at 36°F
last March 23, first November 23
Median at 32°F
last March 8, first December 5
Median at 28°F
last February 19, first December 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°FApr 8Apr 3Mar 30Mar 26Mar 23Mar 19Mar 15Mar 10Mar 3
32°FMar 28Mar 22Mar 17Mar 13Mar 8Mar 4Feb 28Feb 24Feb 12
28°FMar 15Mar 6Mar 1Feb 25Feb 19Feb 12Feb 7Feb 2Jan 26
24°FFeb 28Feb 20Feb 10Feb 5Feb 1Jan 29Jan 23Jan 16Jan 9
20°FFeb 13Feb 4Jan 31Jan 28Jan 23Jan 19Jan 15Jan 10Jan 3
16°FFeb 6Feb 1Jan 30Jan 27Jan 22Jan 17Jan 15Jan 12Jan 8

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

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°F269261255249245239234228218
32°F301292284278272266260252244
28°F334324314307303297290283274
24°F365355345338332325317309301
20°F365365365365358350342334324
16°F365365365365365365365360339

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
89% of years
20°F or colder
58% of years
16°F or colder
23% 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
2,596
Cooling degree days, base 65°F
2,026
Growing degree days, base 40°F
8,684
Growing degree days, base 45°F
7,041
Growing degree days, base 50°F
5,534
Growing degree days, base 55°F
4,193
Growing degree days, base 60°F
3,022

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January627157
February507264
March37712169
April14360375
May29190626
June2384832
July0507972
August0460925
September4302748
October8591473
November29514206
December528386

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 9.1 km from Aurora. 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 USC00310375 (Aurora 6 N). Public domain.