Lisbon climate

Lisbon Frost Dates and Growing Season

NOAA 1991-2020 normals for London Fish Hatchery, 11.4 km from Lisbon, elevation 1120 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for London Fish Hatchery. 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 April 24 and the first fall freeze around October 18, a growing season of about 175 days.

Median at 36°F
last May 4, first October 7
Median at 32°F
last April 24, first October 18
Median at 28°F
last April 14, first October 29

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 20May 15May 10May 7May 4May 1Apr 28Apr 24Apr 20
32°FMay 10May 4Apr 30Apr 27Apr 24Apr 21Apr 19Apr 15Apr 10
28°FApr 30Apr 24Apr 19Apr 17Apr 14Apr 10Apr 7Apr 4Mar 31
24°FApr 16Apr 11Apr 5Apr 3Mar 31Mar 30Mar 25Mar 21Mar 16
20°FApr 4Mar 31Mar 29Mar 25Mar 22Mar 19Mar 15Mar 11Mar 5
16°FMar 28Mar 23Mar 18Mar 15Mar 11Mar 7Mar 4Feb 28Feb 23

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 23Sep 29Oct 1Oct 4Oct 7Oct 9Oct 11Oct 15Oct 20
32°FOct 5Oct 8Oct 11Oct 15Oct 18Oct 21Oct 23Oct 27Nov 1
28°FOct 15Oct 19Oct 23Oct 26Oct 29Nov 1Nov 3Nov 7Nov 12
24°FOct 25Oct 31Nov 2Nov 5Nov 8Nov 12Nov 16Nov 20Nov 27
20°FNov 3Nov 9Nov 13Nov 17Nov 21Nov 26Nov 30Dec 3Dec 10
16°FNov 14Nov 20Nov 25Nov 30Dec 2Dec 6Dec 11Dec 17Dec 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°F174168163159155152148143136
32°F195189184180175171167163157
28°F219211206202198193189183176
24°F246236229224220215210205199
20°F270260255250244240234228219
16°F293284278273268263257249240

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
6,040
Cooling degree days, base 65°F
741
Growing degree days, base 40°F
5,237
Growing degree days, base 45°F
4,062
Growing degree days, base 50°F
3,022
Growing degree days, base 55°F
2,123
Growing degree days, base 60°F
1,362

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21203
February1,01803
March835129
April4615111
May19153341
June32165584
July7236694
August12188642
September10784430
October39610153
November726030
December1,04603

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 11.4 km from Lisbon. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00334681 (London Fish Hatchery). Public domain.