Scappoose climate

Scappoose Frost Dates and Growing Season

NOAA 1991-2020 normals for Scappoose Ind AP, 2.5 km from Scappoose, elevation 55 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Scappoose Ind 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 April 10 and the first fall freeze around November 2, a growing season of about 209 days.

Median at 36°F
last April 30, first October 16
Median at 32°F
last April 10, first November 2
Median at 28°F
last March 3, first November 19

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 17May 11May 6May 3Apr 30Apr 28Apr 26Apr 22Apr 15
32°FMay 1Apr 25Apr 19Apr 14Apr 10Apr 4Mar 30Mar 24Mar 17
28°FMar 28Mar 19Mar 12Mar 7Mar 3Feb 27Feb 23Feb 16Feb 2
24°FFeb 28Feb 25Feb 18Feb 12Feb 2Jan 24Jan 13Jan 4Dec 19
20°FFeb 19Feb 6Jan 26Jan 15Jan 6Dec 31Dec 20Dec 11Dec 3
16°FFeb 8Jan 18Jan 3Dec 31Dec 21Dec 14Dec 11Dec 7Dec 2

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 1Oct 4Oct 8Oct 12Oct 16Oct 20Oct 23Oct 28Nov 3
32°FOct 16Oct 22Oct 26Oct 30Nov 2Nov 6Nov 10Nov 15Nov 23
28°FOct 31Nov 5Nov 10Nov 14Nov 19Nov 23Nov 30Dec 6Dec 15
24°FNov 9Nov 18Nov 24Dec 1Dec 7Dec 14Dec 24Jan 1Jan 16
20°FNov 21Dec 1Dec 6Dec 10Dec 18Dec 26Jan 2Jan 13Feb 5
16°FDec 1Dec 5Dec 8Dec 11Dec 16Dec 24Jan 1Jan 12Jan 31

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°F191183178173169164160154148
32°F238227219215209204198191182
28°F300285274267259253246238226
24°F357342331320313306296283269
20°F365365365362351340333323310
16°F365365365365365365365356336

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
95% of years
20°F or colder
60% of years
16°F or colder
27% 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
4,692
Cooling degree days, base 65°F
335
Growing degree days, base 40°F
4,956
Growing degree days, base 45°F
3,497
Growing degree days, base 50°F
2,345
Growing degree days, base 55°F
1,451
Growing degree days, base 60°F
779

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January76602
February62403
March571023
April437172
May25311232
June13035356
July31116550
August25124564
September10345392
October3682130
November606018
December77803

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 2.5 km from Scappoose. 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 USW00004201 (Scappoose Ind AP). Public domain.