Malheur County climate

Malheur County Frost Dates and Growing Season

NOAA 1991-2020 normals for Rome 2 Nw, 37.2 km from Malheur County, elevation 3405 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rome 2 Nw. 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 June 11 and the first fall freeze around September 10, a growing season of about 88 days.

Median at 32°F
last June 11, first September 10
Median at 28°F
last May 22, first September 21

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°F–––––––––
32°FJul 3Jun 25Jun 20Jun 15Jun 11Jun 7Jun 2May 29May 20
28°FJun 19Jun 8Jun 2May 28May 22May 18May 14May 9May 4
24°FMay 31May 19May 14May 9May 6May 3May 1Apr 27Apr 21
20°FMay 15May 7May 2Apr 29Apr 26Apr 22Apr 18Apr 13Apr 6
16°FMay 3Apr 24Apr 19Apr 13Apr 9Apr 4Mar 31Mar 25Mar 15

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°F–––––––––
32°FAug 27Sep 1Sep 4Sep 7Sep 10Sep 12Sep 15Sep 19Sep 24
28°FSep 7Sep 11Sep 15Sep 19Sep 21Sep 24Sep 28Oct 1Oct 5
24°FSep 18Sep 23Sep 26Sep 30Oct 2Oct 4Oct 8Oct 11Oct 17
20°FSep 29Oct 3Oct 6Oct 10Oct 14Oct 18Oct 22Oct 26Nov 1
16°FOct 8Oct 15Oct 19Oct 24Oct 28Oct 31Nov 3Nov 7Nov 14

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°F877973686459544738
32°F11410499938884787161
28°F1431351291241181121059784
24°F170162155150146141136130117
20°F195188182176171166160153142
16°F229219212207200194188181169

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
6,353
Cooling degree days, base 65°F
484
Growing degree days, base 40°F
4,383
Growing degree days, base 45°F
3,255
Growing degree days, base 50°F
2,322
Growing degree days, base 55°F
1,557
Growing degree days, base 60°F
944

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,10000
February84801
March72909
April543045
May30911200
June11362401
July12223676
August24160602
September17228315
October524069
November84905
December1,13000

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 37.2 km from Malheur County. 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 USC00357310 (Rome 2 Nw). Public domain.