Vaughn climate

Vaughn Frost Dates and Growing Season

NOAA 1991-2020 normals for Great Falls Intl AP, 15.7 km from Vaughn, elevation 3664 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Great Falls Intl 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 May 19 and the first fall freeze around September 24, a growing season of about 126 days.

Median at 36°F
last June 5, first September 12
Median at 32°F
last May 19, first September 24
Median at 28°F
last May 5, first October 3

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 25Jun 17Jun 12Jun 8Jun 5Jun 2May 30May 27May 22
32°FJun 2May 29May 25May 22May 19May 16May 14May 11May 7
28°FMay 18May 13May 10May 8May 5May 3May 1Apr 29Apr 23
24°FMay 8May 3Apr 30Apr 27Apr 24Apr 21Apr 17Apr 12Apr 6
20°FMay 1Apr 26Apr 21Apr 17Apr 13Apr 9Apr 5Apr 2Mar 27
16°FApr 25Apr 17Apr 13Apr 8Apr 5Apr 2Mar 30Mar 23Mar 16

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°FAug 27Sep 2Sep 6Sep 10Sep 12Sep 15Sep 18Sep 22Sep 26
32°FSep 9Sep 15Sep 19Sep 22Sep 24Sep 27Sep 29Oct 1Oct 5
28°FSep 20Sep 26Sep 29Oct 1Oct 3Oct 6Oct 9Oct 13Oct 18
24°FSep 30Oct 3Oct 6Oct 10Oct 13Oct 16Oct 20Oct 24Oct 29
20°FOct 4Oct 10Oct 14Oct 18Oct 23Oct 26Oct 30Nov 2Nov 8
16°FOct 11Oct 17Oct 23Oct 28Nov 1Nov 3Nov 6Nov 11Nov 18

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°F1171111061019692877969
32°F143136132129126122118113107
28°F168162157153149146142138132
24°F195187181176172167163156150
20°F217208203197192186181175165
16°F235227219213209204198191182

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
7,722
Cooling degree days, base 65°F
310
Growing degree days, base 40°F
3,724
Growing degree days, base 45°F
2,693
Growing degree days, base 50°F
1,848
Growing degree days, base 55°F
1,174
Growing degree days, base 60°F
662

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,23501
February1,08502
March95807
April678025
May4223124
June19324288
July48136553
August66120522
September25825251
October628264
November941011
December1,21000

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 15.7 km from Vaughn. 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 USW00024143 (Great Falls Intl AP). Public domain.