Ireton climate

Ireton Frost Dates and Growing Season

NOAA 1991-2020 normals for Hawarden, 13.9 km from Ireton, elevation 1190 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hawarden. 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 May 1 and the first fall freeze around October 4, a growing season of about 155 days.

Median at 36°F
last May 8, first September 26
Median at 32°F
last May 1, first October 4
Median at 28°F
last April 22, first October 16

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 24May 18May 14May 11May 8May 6May 4May 1Apr 27
32°FMay 14May 9May 6May 4May 1Apr 30Apr 26Apr 22Apr 17
28°FMay 4Apr 30Apr 28Apr 25Apr 22Apr 19Apr 16Apr 12Apr 8
24°FApr 26Apr 21Apr 18Apr 15Apr 12Apr 9Apr 6Apr 2Mar 28
20°FApr 19Apr 14Apr 9Apr 6Apr 4Apr 1Mar 29Mar 24Mar 18
16°FApr 11Apr 6Apr 2Mar 30Mar 26Mar 22Mar 18Mar 13Mar 8

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 14Sep 18Sep 21Sep 24Sep 26Sep 29Oct 1Oct 4Oct 9
32°FSep 21Sep 26Sep 29Oct 1Oct 4Oct 7Oct 10Oct 14Oct 18
28°FSep 30Oct 4Oct 9Oct 13Oct 16Oct 19Oct 21Oct 24Oct 29
24°FOct 12Oct 17Oct 21Oct 23Oct 26Oct 29Oct 31Nov 3Nov 7
20°FOct 20Oct 26Oct 30Nov 1Nov 3Nov 5Nov 8Nov 10Nov 16
16°FOct 30Nov 2Nov 5Nov 8Nov 10Nov 13Nov 16Nov 20Nov 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°F155150146142139135132127122
32°F173168163159155151148143138
28°F193186182178174170166162155
24°F214207202198193190186181175
20°F232224219215211207203199192
16°F252245239233229224219213205

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
7,410
Cooling degree days, base 65°F
767
Growing degree days, base 40°F
4,852
Growing degree days, base 45°F
3,801
Growing degree days, base 50°F
2,862
Growing degree days, base 55°F
2,040
Growing degree days, base 60°F
1,338

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,48600
February1,21401
March966115
April556478
May23742294
June36168582
July7271728
August15201651
September14174393
October4996110
November921010
December1,33100

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 13.9 km from Ireton. 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 USC00133718 (Hawarden). Public domain.