Roseburg North climate

Roseburg North Frost Dates and Growing Season

NOAA 1991-2020 normals for Winchester, 1.5 km from Roseburg North, elevation 460 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Winchester. 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 31 and the first fall freeze around November 5, a growing season of about 215 days.

Median at 36°F
last April 28, first October 20
Median at 32°F
last March 31, first November 5
Median at 28°F
last February 26, first December 1

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 15May 9May 4May 1Apr 28Apr 24Apr 20Apr 14Apr 6
32°FApr 26Apr 18Apr 10Apr 4Mar 31Mar 27Mar 22Mar 14Mar 5
28°FMar 31Mar 19Mar 9Mar 3Feb 26Feb 20Feb 13Feb 1Jan 11
24°FFeb 24Feb 17Feb 5Jan 29Jan 20Jan 6Dec 30Dec 18Nov 30
20°FFeb 15Jan 25Jan 13Jan 1Dec 30Dec 25Dec 20Dec 13Dec 5
16°F–––––––––

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 2Oct 8Oct 13Oct 17Oct 20Oct 23Oct 27Oct 31Nov 6
32°FOct 16Oct 23Oct 28Nov 1Nov 5Nov 9Nov 15Nov 24Dec 3
28°FOct 29Nov 7Nov 14Nov 24Dec 1Dec 6Dec 16Dec 25Jan 10
24°FNov 12Nov 30Dec 5Dec 14Dec 21Dec 30Jan 6Jan 23Feb 8
20°FDec 1Dec 8Dec 16Dec 21Dec 25Dec 30Jan 4Jan 19Feb 11
16°F–––––––––

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°F199191185180175169164157149
32°F254241230222215210203196187
28°F325309298288278269259249236
24°F365365365354343334327313303
20°F365365365365365365365360342
16°F365365365365365365365365365

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
98% of years
24°F or colder
66% of years
20°F or colder
25% of years
16°F or colder
7% 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
4,168
Cooling degree days, base 65°F
488
Growing degree days, base 40°F
5,553
Growing degree days, base 45°F
4,003
Growing degree days, base 50°F
2,741
Growing degree days, base 55°F
1,764
Growing degree days, base 60°F
1,023

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January70205
February568012
March527037
April394197
May22417262
June9354411
July11178632
August10170625
September7463440
October3055182
November542032
December71807

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 1.5 km from Roseburg North. 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 USC00359461 (Winchester). Public domain.