Mill Creek climate

Mill Creek Frost Dates and Growing Season

NOAA 1991-2020 normals for Kumbrabow, 15 km from Mill Creek, elevation 3235 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Kumbrabow. 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 7 and the first fall freeze around October 6, a growing season of about 150 days.

Median at 36°F
last May 21, first September 27
Median at 32°F
last May 7, first October 6
Median at 28°F
last April 26, first October 18

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°FJun 5Jun 1May 29May 25May 21May 17May 13May 8May 3
32°FMay 26May 19May 16May 11May 7May 4May 1Apr 28Apr 22
28°FMay 14May 7May 2Apr 30Apr 26Apr 23Apr 20Apr 18Apr 15
24°FMay 1Apr 25Apr 20Apr 18Apr 15Apr 13Apr 10Apr 7Apr 3
20°FApr 17Apr 13Apr 10Apr 7Apr 5Apr 3Apr 1Mar 29Mar 24
16°FApr 9Apr 5Apr 2Mar 31Mar 29Mar 26Mar 23Mar 19Mar 13

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 12Sep 18Sep 21Sep 24Sep 27Sep 30Oct 2Oct 5Oct 9
32°FSep 22Sep 27Oct 1Oct 3Oct 6Oct 9Oct 12Oct 16Oct 20
28°FOct 3Oct 9Oct 13Oct 16Oct 18Oct 22Oct 24Oct 27Oct 31
24°FOct 15Oct 21Oct 24Oct 27Oct 29Oct 31Nov 3Nov 5Nov 10
20°FOct 26Oct 31Nov 2Nov 5Nov 7Nov 10Nov 13Nov 16Nov 21
16°FNov 4Nov 7Nov 10Nov 14Nov 17Nov 20Nov 25Nov 29Dec 5

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°F149143137132128124120113106
32°F171164159154150146140135128
28°F194187182178173169163159151
24°F214208204201197192188182175
20°F235228223219216212209205199
16°F257248243239235231225221215

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
6,977
Cooling degree days, base 65°F
137
Growing degree days, base 40°F
3,899
Growing degree days, base 45°F
2,816
Growing degree days, base 50°F
1,887
Growing degree days, base 55°F
1,113
Growing degree days, base 60°F
509

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,23801
February99101
March95208
April593162
May3164197
June13020343
July4658477
August6944440
September20810265
October512182
November81609
December1,10702

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 15 km from Mill Creek. 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 USC00464971 (Kumbrabow). Public domain.