Smithfield climate

Smithfield Frost Dates and Growing Season

NOAA 1991-2020 normals for New Sharon, 13.6 km from Smithfield, elevation 480 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for New Sharon. 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 7 and the first fall freeze around October 2, a growing season of about 146 days.

Median at 36°F
last May 20, first September 22
Median at 32°F
last May 7, first October 2
Median at 28°F
last April 26, first October 15

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°FJun 3May 29May 25May 23May 20May 17May 14May 12May 7
32°FMay 22May 16May 13May 10May 7May 5May 3Apr 30Apr 28
28°FMay 5May 2Apr 30Apr 29Apr 26Apr 24Apr 22Apr 18Apr 13
24°FApr 25Apr 21Apr 18Apr 16Apr 13Apr 10Apr 8Apr 6Apr 3
20°FApr 15Apr 11Apr 8Apr 6Apr 4Apr 3Apr 1Mar 30Mar 24
16°FApr 7Apr 4Apr 2Apr 1Mar 30Mar 27Mar 24Mar 21Mar 17

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 9Sep 13Sep 16Sep 19Sep 22Sep 24Sep 27Sep 30Oct 4
32°FSep 20Sep 24Sep 27Sep 30Oct 2Oct 5Oct 8Oct 11Oct 17
28°FOct 1Oct 5Oct 9Oct 12Oct 15Oct 18Oct 21Oct 26Oct 31
24°FOct 13Oct 19Oct 23Oct 26Oct 30Nov 1Nov 3Nov 6Nov 10
20°FOct 28Nov 1Nov 3Nov 6Nov 8Nov 11Nov 13Nov 17Nov 21
16°FNov 7Nov 11Nov 14Nov 16Nov 19Nov 21Nov 24Nov 27Dec 1

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°F141135131127123120115111105
32°F163157152149146143139134127
28°F189183179175172168164159152
24°F213208204201198194191187180
20°F233228225221218215212209203
16°F251244240237234231228224219

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
8,129
Cooling degree days, base 65°F
275
Growing degree days, base 40°F
3,737
Growing degree days, base 45°F
2,778
Growing degree days, base 50°F
1,944
Growing degree days, base 55°F
1,239
Growing degree days, base 60°F
676

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,47800
February1,27400
March1,13805
April719019
May3708151
June13241362
July25113553
August3782510
September20931285
October575155
November90905
December1,26300

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 13.6 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 USC00175736 (New Sharon). Public domain.