Troy Frost Dates and Growing Season

NOAA 1991-2020 normals for Moscow U Of I, 14.2 km from Troy, elevation 2660 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Moscow U Of I. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

NOAA does not state freeze dates for this station.

Median at 28°F: last May 14, first September 23

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Jun 8	May 29	May 24	May 18	May 14	May 10	May 6	May 2	Apr 27
24°F	May 12	May 5	May 1	Apr 26	Apr 22	Apr 16	Apr 10	Apr 1	Mar 24
20°F	Apr 21	Apr 7	Mar 31	Mar 24	Mar 18	Mar 13	Mar 9	Mar 5	Feb 28
16°F	Mar 21	Mar 15	Mar 10	Mar 6	Mar 2	Feb 27	Feb 23	Feb 16	Feb 7

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Sep 6	Sep 12	Sep 16	Sep 20	Sep 23	Sep 26	Sep 29	Oct 3	Oct 9
24°F	Sep 20	Sep 27	Sep 30	Oct 3	Oct 6	Oct 10	Oct 16	Oct 21	Oct 30
20°F	Oct 4	Oct 11	Oct 17	Oct 21	Oct 25	Oct 31	Nov 5	Nov 13	Nov 22
16°F	Oct 18	Oct 27	Nov 1	Nov 6	Nov 12	Nov 18	Nov 24	Nov 29	Dec 7

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	69	58	52	46	41	37	32	28	23
32°F	115	105	98	91	85	79	72	64	53
28°F	157	149	143	138	133	127	122	115	103
24°F	204	192	184	177	171	164	158	150	142
20°F	249	239	231	223	216	209	203	195	183
16°F	289	277	268	260	253	246	240	232	220

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: 6,948
Cooling degree days, base 65°F: 196
Growing degree days, base 40°F: 3,553
Growing degree days, base 45°F: 2,506
Growing degree days, base 50°F: 1,648
Growing degree days, base 55°F: 980
Growing degree days, base 60°F: 495

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,091	0	0
February	899	0	0
March	805	0	3
April	600	0	27
May	388	3	131
June	232	13	238
July	80	75	460
August	72	84	478
September	232	21	255
October	569	0	54
November	866	0	3
December	1,116	0	0

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 14.2 km from Troy. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00106152 (Moscow U Of I). Public domain.