Brighton climate

Brighton Frost Dates and Growing Season

NOAA 1991-2020 normals for Milford Gm Proving Ground, 9.6 km from Brighton, elevation 970 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Milford Gm Proving Ground. 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 6 and the first fall freeze around October 12, a growing season of about 157 days.

Median at 36°F
last May 18, first October 1
Median at 32°F
last May 6, first October 12
Median at 28°F
last April 26, 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 31May 27May 24May 21May 18May 14May 10May 5Apr 30
32°FMay 22May 17May 13May 9May 6May 3Apr 30Apr 26Apr 21
28°FMay 11May 6May 3Apr 29Apr 26Apr 23Apr 20Apr 16Apr 11
24°FMay 1Apr 26Apr 21Apr 19Apr 15Apr 12Apr 9Apr 5Apr 1
20°FApr 19Apr 14Apr 9Apr 6Apr 4Apr 1Mar 30Mar 27Mar 19
16°FApr 7Apr 2Mar 31Mar 28Mar 25Mar 22Mar 18Mar 14Mar 9

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 23Sep 26Sep 29Oct 1Oct 4Oct 7Oct 11Oct 15
32°FSep 27Oct 1Oct 5Oct 9Oct 12Oct 14Oct 18Oct 22Oct 27
28°FOct 8Oct 14Oct 18Oct 21Oct 24Oct 27Oct 30Nov 2Nov 6
24°FOct 21Oct 27Oct 30Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17
20°FNov 2Nov 5Nov 8Nov 12Nov 14Nov 17Nov 21Nov 25Dec 1
16°FNov 9Nov 15Nov 20Nov 23Nov 26Nov 29Dec 2Dec 7Dec 15

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°F157149144140136133128123118
32°F177171166161157154149144136
28°F199192186182179175169165158
24°F221214210205201197193188181
20°F245237233228224221217212205
16°F270260254249245241236231225

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
6,853
Cooling degree days, base 65°F
572
Growing degree days, base 40°F
4,648
Growing degree days, base 45°F
3,565
Growing degree days, base 50°F
2,617
Growing degree days, base 55°F
1,799
Growing degree days, base 60°F
1,109

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,30800
February1,13201
March955015
April565367
May25935268
June55118513
July12196649
August23155597
September14259373
October4606117
November800017
December1,14201

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 9.6 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 USC00205452 (Milford Gm Proving Ground). Public domain.