Lisbon climate

Lisbon Frost Dates and Growing Season

NOAA 1991-2020 normals for Benton 5 Sw, 20.1 km from Lisbon, elevation 1200 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Benton 5 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 15 and the first fall freeze around September 28, a growing season of about 133 days.

Median at 36°F
last May 31, first September 17
Median at 32°F
last May 15, first September 28
Median at 28°F
last April 30, first October 7

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 14Jun 9Jun 5Jun 2May 31May 27May 23May 20May 15
32°FJun 3May 26May 22May 18May 15May 11May 8May 4May 1
28°FMay 16May 10May 5May 2Apr 30Apr 28Apr 25Apr 22Apr 18
24°FApr 29Apr 25Apr 23Apr 20Apr 18Apr 16Apr 12Apr 9Apr 6
20°FApr 19Apr 15Apr 11Apr 9Apr 7Apr 5Apr 3Apr 1Mar 29
16°FApr 11Apr 6Apr 4Apr 3Apr 1Mar 31Mar 29Mar 24Mar 19

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

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°F128122117112108104999485
32°F154147141137133129124118110
28°F180173167163159155151145138
24°F206200195191186181177172165
20°F228221217213209205200195190
16°F247240235231228224220216210

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
8,364
Cooling degree days, base 65°F
226
Growing degree days, base 40°F
3,557
Growing degree days, base 45°F
2,608
Growing degree days, base 50°F
1,791
Growing degree days, base 55°F
1,109
Growing degree days, base 60°F
575

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,49101
February1,28700
March1,15303
April727127
May3788154
June14540349
July4693511
August7567458
September25318236
October611048
November91805
December1,28000

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 20.1 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 USC00270681 (Benton 5 Sw). Public domain.