Winthrop climate

Winthrop Frost Dates and Growing Season

NOAA 1991-2020 normals for Lawrenceville 3 Sw, 10.2 km from Winthrop, elevation 466 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lawrenceville 3 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 10 and the first fall freeze around October 5, a growing season of about 148 days.

Median at 36°F
last May 20, first September 23
Median at 32°F
last May 10, first October 5
Median at 28°F
last April 30, first October 16

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 30May 26May 23May 20May 18May 15May 12May 7
32°FMay 25May 20May 16May 13May 10May 7May 4May 1Apr 25
28°FMay 15May 10May 6May 3Apr 30Apr 27Apr 24Apr 20Apr 16
24°FMay 6Apr 30Apr 25Apr 21Apr 18Apr 15Apr 11Apr 8Apr 4
20°FApr 21Apr 17Apr 13Apr 9Apr 7Apr 5Apr 3Mar 31Mar 26
16°FApr 12Apr 7Apr 5Apr 3Apr 1Mar 29Mar 26Mar 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 8Sep 13Sep 17Sep 20Sep 23Sep 27Sep 30Oct 3Oct 8
32°FSep 17Sep 24Sep 29Oct 2Oct 5Oct 8Oct 12Oct 16Oct 22
28°FOct 1Oct 5Oct 9Oct 13Oct 16Oct 20Oct 24Oct 29Nov 4
24°FOct 10Oct 17Oct 23Oct 27Oct 31Nov 2Nov 5Nov 9Nov 14
20°FOct 26Oct 31Nov 3Nov 6Nov 9Nov 11Nov 14Nov 19Nov 24
16°FNov 4Nov 9Nov 12Nov 16Nov 19Nov 22Nov 25Nov 29Dec 3

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°F145137132128124120116111105
32°F169162156152148143138132125
28°F194184179173169164159153145
24°F215208203199193187182177168
20°F234227222218214210206202195
16°F254246240236233229224220213

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
7,669
Cooling degree days, base 65°F
451
Growing degree days, base 40°F
4,290
Growing degree days, base 45°F
3,259
Growing degree days, base 50°F
2,358
Growing degree days, base 55°F
1,581
Growing degree days, base 60°F
937

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,48001
February1,26401
March1,09304
April634248
May28324236
June7794467
July17154603
August35133563
September17341329
October512493
November846014
December1,25501

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 10.2 km from Winthrop. 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 USC00304647 (Lawrenceville 3 Sw). Public domain.