Norfolk climate

Norfolk Frost Dates and Growing Season

NOAA 1991-2020 normals for Walpole 2, 7.9 km from Norfolk, elevation 170 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Walpole 2. 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 27 and the first fall freeze around October 14, a growing season of about 169 days.

Median at 36°F
last May 9, first October 3
Median at 32°F
last April 27, first October 14
Median at 28°F
last April 13, first October 26

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 22May 18May 14May 12May 9May 6May 4May 1Apr 27
32°FMay 11May 6May 3Apr 30Apr 27Apr 24Apr 22Apr 19Apr 15
28°FApr 26Apr 22Apr 19Apr 16Apr 13Apr 9Apr 7Apr 4Apr 1
24°FApr 12Apr 7Apr 4Apr 2Mar 31Mar 30Mar 26Mar 22Mar 17
20°FApr 2Mar 31Mar 29Mar 25Mar 22Mar 19Mar 16Mar 12Mar 7
16°FMar 28Mar 22Mar 19Mar 15Mar 13Mar 10Mar 7Mar 3Feb 25

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 23Sep 27Sep 30Oct 2Oct 3Oct 5Oct 8Oct 12Oct 16
32°FOct 2Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 23Oct 29
28°FOct 11Oct 16Oct 20Oct 23Oct 26Oct 30Nov 1Nov 5Nov 10
24°FOct 23Oct 29Nov 2Nov 4Nov 7Nov 11Nov 14Nov 18Nov 25
20°FNov 5Nov 11Nov 15Nov 18Nov 22Nov 26Dec 1Dec 3Dec 8
16°FNov 19Nov 25Nov 29Dec 2Dec 4Dec 7Dec 11Dec 16Dec 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°F166159154151148145140136129
32°F189182177173169165161156150
28°F215208204200196192188183176
24°F242234229224220217211207200
20°F266258252248243239234229222
16°F290282275271266262257252243

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
5,884
Cooling degree days, base 65°F
727
Growing degree days, base 40°F
5,115
Growing degree days, base 45°F
3,939
Growing degree days, base 50°F
2,916
Growing degree days, base 55°F
2,040
Growing degree days, base 60°F
1,309

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13902
February97001
March848113
April499480
May22330284
June49126527
July4263724
August9218674
September10078430
October3907145
November675032
December97604

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 7.9 km from Norfolk. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00198757 (Walpole 2). Public domain.