Ipswich climate

Ipswich Frost Dates and Growing Season

NOAA 1991-2020 normals for Ipswich, 0.8 km from Ipswich, elevation 1547 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ipswich. 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 8 and the first fall freeze around September 29, a growing season of about 143 days.

Median at 36°F
last May 18, first September 21
Median at 32°F
last May 8, first September 29
Median at 28°F
last April 30, first October 6

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

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 12Sep 16Sep 19Sep 21Sep 23Sep 25Sep 28Oct 2
32°FSep 17Sep 21Sep 24Sep 26Sep 29Oct 1Oct 3Oct 6Oct 12
28°FSep 24Sep 28Oct 1Oct 4Oct 6Oct 9Oct 13Oct 16Oct 20
24°FOct 1Oct 6Oct 10Oct 13Oct 16Oct 19Oct 22Oct 25Oct 29
20°FOct 10Oct 16Oct 20Oct 23Oct 26Oct 29Nov 1Nov 3Nov 8
16°FOct 22Oct 26Oct 30Nov 1Nov 4Nov 6Nov 9Nov 13Nov 19

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°F142135131128124121118113108
32°F161154150147143139135131125
28°F178173168164160156153148142
24°F196192186182178175169164156
20°F215209204200196192187182176
16°F234227222218213209205200193

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
8,288
Cooling degree days, base 65°F
549
Growing degree days, base 40°F
4,309
Growing degree days, base 45°F
3,322
Growing degree days, base 50°F
2,446
Growing degree days, base 55°F
1,686
Growing degree days, base 60°F
1,051

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,60400
February1,32700
March1,08405
April638145
May29122236
June58106498
July13216668
August28158595
September18744321
October592373
November1,02603
December1,44000

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 0.8 km from Ipswich. 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 USC00394206 (Ipswich). Public domain.