Lisbon climate

Lisbon Frost Dates and Growing Season

NOAA 1991-2020 normals for Lisbon, 0.9 km from Lisbon, elevation 1149 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lisbon. 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 12 and the first fall freeze around September 27, a growing season of about 136 days.

Median at 36°F
last May 21, first September 19
Median at 32°F
last May 12, first September 27
Median at 28°F
last May 3, first October 4

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 24May 21May 19May 17May 14May 10
32°FMay 23May 20May 17May 14May 12May 9May 7May 4Apr 30
28°FMay 15May 10May 7May 5May 3Apr 30Apr 28Apr 25Apr 20
24°FMay 5May 1Apr 28Apr 25Apr 22Apr 20Apr 17Apr 13Apr 10
20°FApr 28Apr 23Apr 19Apr 16Apr 13Apr 11Apr 8Apr 5Apr 1
16°FApr 21Apr 16Apr 12Apr 9Apr 6Apr 3Apr 1Mar 30Mar 24

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 6Sep 10Sep 14Sep 16Sep 19Sep 21Sep 23Sep 26Sep 30
32°FSep 14Sep 19Sep 22Sep 25Sep 27Sep 29Oct 1Oct 4Oct 8
28°FSep 23Sep 27Sep 30Oct 2Oct 4Oct 7Oct 10Oct 14Oct 18
24°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 18Oct 21Oct 25Oct 29
20°FOct 8Oct 13Oct 18Oct 22Oct 26Oct 28Nov 1Nov 3Nov 8
16°FOct 19Oct 26Oct 29Nov 1Nov 3Nov 6Nov 9Nov 13Nov 17

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°F134129125121118115111106100
32°F153148144140136132129124118
28°F171166162159155152148144137
24°F192187182177173170166161154
20°F213206201197193189184179171
16°F229223218214210206201196189

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
9,014
Cooling degree days, base 65°F
462
Growing degree days, base 40°F
3,991
Growing degree days, base 45°F
3,056
Growing degree days, base 50°F
2,230
Growing degree days, base 55°F
1,517
Growing degree days, base 60°F
921

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,73300
February1,44100
March1,18901
April712129
May33018209
June7992465
July19180626
August41134558
September21936288
October648252
November1,08302
December1,52200

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 0.9 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 USC00325220 (Lisbon). Public domain.