Brighton climate

Brighton Frost Dates and Growing Season

NOAA 1991-2020 normals for Jerseyville 2 Sw, 18.8 km from Brighton, elevation 630 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jerseyville 2 Sw. 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 14 and the first fall freeze around October 19, a growing season of about 187 days.

Median at 36°F
last April 26, first October 11
Median at 32°F
last April 14, first October 19
Median at 28°F
last April 4, first October 30

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 10May 5May 2Apr 29Apr 26Apr 23Apr 20Apr 16Apr 12
32°FApr 30Apr 25Apr 21Apr 17Apr 14Apr 11Apr 8Apr 5Mar 31
28°FApr 19Apr 13Apr 9Apr 7Apr 4Apr 1Mar 30Mar 25Mar 19
24°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 21Mar 18Mar 14Mar 8
20°FMar 30Mar 24Mar 20Mar 17Mar 14Mar 10Mar 7Mar 2Feb 26
16°FMar 22Mar 17Mar 12Mar 8Mar 5Mar 2Feb 26Feb 20Feb 10

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 26Sep 30Oct 4Oct 8Oct 11Oct 13Oct 16Oct 18Oct 22
32°FOct 7Oct 12Oct 15Oct 17Oct 19Oct 22Oct 25Oct 28Nov 1
28°FOct 18Oct 22Oct 25Oct 28Oct 30Nov 1Nov 4Nov 8Nov 14
24°FOct 28Nov 1Nov 3Nov 6Nov 10Nov 13Nov 17Nov 22Nov 28
20°FNov 4Nov 10Nov 14Nov 18Nov 22Nov 26Dec 1Dec 4Dec 11
16°FNov 13Nov 20Nov 25Nov 30Dec 3Dec 7Dec 12Dec 17Dec 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°F184177173170166161157152146
32°F206200196191187183179175168
28°F230223217213208205201196189
24°F254245241236231227222217211
20°F279270264259253247243237228
16°F299289284278273268263255247

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
5,348
Cooling degree days, base 65°F
1,152
Growing degree days, base 40°F
6,072
Growing degree days, base 45°F
4,823
Growing degree days, base 50°F
3,714
Growing degree days, base 55°F
2,728
Growing degree days, base 60°F
1,871

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,15403
February92007
March710251
April36215180
May12192440
June14249685
July1350814
August4291752
September70129511
October32623217
November664149
December1,00106

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 18.8 km from Brighton. 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 USC00114489 (Jerseyville 2 Sw). Public domain.