Lisbon climate

Lisbon Frost Dates and Growing Season

NOAA 1991-2020 normals for Durham, 3.6 km from Lisbon, elevation 140 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Durham. 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 15 and the first fall freeze around October 2, a growing season of about 139 days.

Median at 36°F
last May 28, first September 21
Median at 32°F
last May 15, first October 2
Median at 28°F
last May 3, first October 13

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

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°F132127123120116113110106100
32°F157151147143139136132127122
28°F184176171167163159155150145
24°F211204199195191187183177170
20°F236230225221217213209205198
16°F258252247243239236232227222

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
7,921
Cooling degree days, base 65°F
257
Growing degree days, base 40°F
3,683
Growing degree days, base 45°F
2,704
Growing degree days, base 50°F
1,872
Growing degree days, base 55°F
1,178
Growing degree days, base 60°F
631

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,44500
February1,23500
March1,07902
April695018
May3915131
June13342361
July28109545
August5179493
September21822265
October562152
November86404
December1,22100

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 3.6 km from Lisbon. 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 USC00172048 (Durham). Public domain.