Norfolk climate

Norfolk Frost Dates and Growing Season

NOAA 1991-2020 normals for Norfolk 2 Sw, 2.9 km from Norfolk, elevation 1340 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Norfolk 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 May 3 and the first fall freeze around October 11, a growing season of about 161 days.

Median at 36°F
last May 15, first October 2
Median at 32°F
last May 3, first October 11
Median at 28°F
last April 20, first October 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°FMay 28May 25May 21May 18May 15May 11May 9May 6May 2
32°FMay 17May 13May 9May 6May 3May 1Apr 29Apr 25Apr 21
28°FMay 6Apr 30Apr 26Apr 23Apr 20Apr 17Apr 14Apr 11Apr 7
24°FApr 20Apr 16Apr 13Apr 10Apr 7Apr 5Apr 4Apr 2Mar 30
20°FApr 10Apr 6Apr 4Apr 2Mar 31Mar 30Mar 27Mar 22Mar 18
16°FApr 2Mar 31Mar 28Mar 25Mar 22Mar 19Mar 17Mar 13Mar 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°FSep 20Sep 24Sep 27Sep 30Oct 2Oct 4Oct 6Oct 9Oct 14
32°FOct 1Oct 3Oct 6Oct 9Oct 11Oct 14Oct 18Oct 22Oct 28
28°FOct 9Oct 13Oct 18Oct 21Oct 25Oct 28Nov 1Nov 4Nov 8
24°FOct 22Oct 27Oct 31Nov 2Nov 5Nov 8Nov 11Nov 14Nov 19
20°FNov 2Nov 8Nov 11Nov 14Nov 17Nov 21Nov 24Nov 28Dec 2
16°FNov 13Nov 18Nov 22Nov 24Nov 27Nov 30Dec 3Dec 6Dec 13

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°F157151147143139136133128122
32°F181174169165161157153150144
28°F207199195191187183179174167
24°F230223219215210207203199192
20°F251244238235230227223218212
16°F271263258254249245240236230

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
7,311
Cooling degree days, base 65°F
370
Growing degree days, base 40°F
4,119
Growing degree days, base 45°F
3,089
Growing degree days, base 50°F
2,192
Growing degree days, base 55°F
1,434
Growing degree days, base 60°F
820

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,33401
February1,15200
March1,03506
April633347
May31516202
June9866420
July20143587
August38108535
September18533308
October526275
November824012
December1,15201

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 2.9 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 USC00065445 (Norfolk 2 Sw). Public domain.