North Portland climate

North Portland Frost Dates and Growing Season

NOAA 1991-2020 normals for Vancouver Pearson AP, 3.8 km from North Portland, elevation 30 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Vancouver Pearson AP. 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 March 29 and the first fall freeze around November 9, a growing season of about 223 days.

Median at 36°F
last April 24, first October 24
Median at 32°F
last March 29, first November 9
Median at 28°F
last March 3, first November 26

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 10May 3Apr 30Apr 27Apr 24Apr 20Apr 15Apr 11Apr 3
32°FApr 18Apr 12Apr 5Apr 2Mar 29Mar 25Mar 20Mar 14Mar 6
28°FMar 27Mar 18Mar 12Mar 7Mar 3Feb 27Feb 23Feb 18Feb 4
24°FMar 1Feb 24Feb 19Feb 14Feb 7Jan 31Jan 21Jan 9Dec 26
20°FFeb 21Feb 11Feb 1Jan 25Jan 16Jan 7Dec 30Dec 18Dec 6
16°FFeb 8Jan 27Jan 17Jan 7Dec 30Dec 25Dec 19Dec 10Dec 3

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°FOct 7Oct 13Oct 17Oct 21Oct 24Oct 28Oct 31Nov 5Nov 12
32°FOct 22Oct 29Nov 1Nov 5Nov 9Nov 13Nov 17Nov 23Nov 30
28°FNov 3Nov 11Nov 17Nov 22Nov 26Dec 1Dec 6Dec 12Dec 22
24°FNov 16Nov 25Dec 1Dec 7Dec 14Dec 22Dec 28Jan 5Jan 24
20°FNov 27Dec 3Dec 10Dec 18Dec 25Jan 1Jan 7Jan 21Feb 11
16°FDec 1Dec 6Dec 12Dec 19Dec 25Jan 1Jan 6Jan 18Feb 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°F209199193188183179173166159
32°F252244236230223217212207196
28°F300286277271264258252244234
24°F356339329319312305296286273
20°F365365365365355344336328314
16°F365365365365365365365356339

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
94% of years
20°F or colder
56% of years
16°F or colder
22% 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
4,400
Cooling degree days, base 65°F
400
Growing degree days, base 40°F
5,294
Growing degree days, base 45°F
3,791
Growing degree days, base 50°F
2,573
Growing degree days, base 55°F
1,624
Growing degree days, base 60°F
902

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January75303
February61504
March550027
April400188
May22314260
June9643398
July16139589
August13149601
September8451417
October3352153
November564028
December75204

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 3.8 km from North Portland. 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 USW00094298 (Vancouver Pearson AP). Public domain.