Smithfield climate

Smithfield Frost Dates and Growing Season

NOAA 1991-2020 normals for Pike Island(lock & Dam), 15.3 km from Smithfield, elevation 640 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Pike Island(lock & Dam). 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 18 and the first fall freeze around November 1, a growing season of about 196 days.

Median at 36°F
last April 29, first October 21
Median at 32°F
last April 18, first November 1
Median at 28°F
last April 5, first November 10

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 17May 10May 6May 1Apr 29Apr 26Apr 23Apr 21Apr 17
32°FMay 6Apr 29Apr 24Apr 21Apr 18Apr 16Apr 13Apr 9Apr 4
28°FApr 20Apr 16Apr 12Apr 8Apr 5Apr 3Mar 31Mar 28Mar 23
24°FApr 7Apr 3Mar 31Mar 29Mar 26Mar 24Mar 20Mar 16Mar 10
20°FMar 31Mar 26Mar 23Mar 19Mar 16Mar 13Mar 9Mar 5Feb 28
16°FMar 22Mar 16Mar 13Mar 9Mar 5Mar 2Feb 28Feb 21Feb 13

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°FOct 8Oct 13Oct 16Oct 19Oct 21Oct 23Oct 26Oct 29Nov 1
32°FOct 18Oct 23Oct 27Oct 30Nov 1Nov 3Nov 5Nov 9Nov 13
28°FOct 31Nov 3Nov 6Nov 8Nov 10Nov 13Nov 16Nov 19Nov 25
24°FNov 8Nov 11Nov 14Nov 18Nov 21Nov 25Nov 29Dec 2Dec 9
20°FNov 17Nov 22Nov 27Dec 1Dec 3Dec 7Dec 13Dec 19Dec 25
16°FNov 29Dec 4Dec 10Dec 15Dec 19Dec 23Dec 27Dec 31Jan 7

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°F191185181177174170165160152
32°F214208204200196192187182174
28°F238232227222219215212207201
24°F267258251246241237232227220
20°F290282276270265260255248239
16°F312303297293289283279273263

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
5,420
Cooling degree days, base 65°F
853
Growing degree days, base 40°F
5,601
Growing degree days, base 45°F
4,366
Growing degree days, base 50°F
3,274
Growing degree days, base 55°F
2,325
Growing degree days, base 60°F
1,517

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,09403
February93203
March786029
April4234128
May17049353
June26164588
July2273736
August3242704
September62107496
October33014191
November650037
December94207

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 15.3 km from Smithfield. 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 USC00467018 (Pike Island(lock & Dam)). Public domain.