Bristol climate

Bristol Frost Dates and Growing Season

NOAA 1991-2020 normals for S Lincoln, 10.8 km from Bristol, elevation 1341 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for S Lincoln. 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 21 and the first fall freeze around September 25, a growing season of about 124 days.

Median at 36°F
last June 4, first September 12
Median at 32°F
last May 21, first September 25
Median at 28°F
last May 8, first October 5

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 25Jun 14Jun 10Jun 6Jun 4Jun 1May 29May 24May 20
32°FJun 6Jun 1May 28May 24May 21May 19May 16May 11May 6
28°FMay 23May 18May 14May 11May 8May 5May 1Apr 29Apr 25
24°FMay 11May 6May 2Apr 29Apr 26Apr 23Apr 20Apr 17Apr 12
20°FMay 1Apr 24Apr 20Apr 17Apr 14Apr 12Apr 9Apr 7Apr 4
16°FApr 18Apr 13Apr 10Apr 8Apr 6Apr 4Apr 3Mar 31Mar 27

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°FAug 21Aug 31Sep 4Sep 9Sep 12Sep 15Sep 18Sep 22Sep 27
32°FSep 8Sep 14Sep 18Sep 22Sep 25Sep 28Oct 1Oct 3Oct 7
28°FSep 20Sep 27Oct 1Oct 3Oct 5Oct 8Oct 12Oct 16Oct 22
24°FOct 3Oct 7Oct 11Oct 16Oct 20Oct 23Oct 28Oct 31Nov 3
20°FOct 17Oct 24Oct 28Oct 31Nov 1Nov 4Nov 7Nov 11Nov 15
16°FOct 31Nov 2Nov 6Nov 9Nov 11Nov 14Nov 17Nov 20Nov 24

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°F1211131081039893888170
32°F146139133129124119115111103
28°F169163159155151146142136129
24°F197189184179175171167161154
20°F218211207204200195191186179
16°F237230225222218214210206201

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
8,791
Cooling degree days, base 65°F
155
Growing degree days, base 40°F
3,298
Growing degree days, base 45°F
2,378
Growing degree days, base 50°F
1,588
Growing degree days, base 55°F
938
Growing degree days, base 60°F
453

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,53000
February1,33000
March1,21103
April769124
May4187136
June17531313
July7364456
August10739397
September29414206
October641045
November93807
December1,30700

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 10.8 km from Bristol. 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 USC00437612 (S Lincoln). Public domain.