USDA Hardiness Zone 5b

Frost Dates for 61376 — Walnut, Illinois

NOAA 1991–2020 normals from Walnut, IL (671 ft), under a mile north.

Updated October 28, 2026

In Walnut, the last spring frost (32°F) is around April 24 in half of years and has passed by May 9 in nine years out of ten. The first fall frost comes around October 14, as early as September 30 one year in ten, leaving a typical freeze-free season of 172 days (NOAA, Walnut, IL).

Last spring frost: April 24
First fall frost: October 14
Growing season: 172 days
Hardiness zone: 5b

First snow: December 1
Last snow: March 16
Winters with snow: 100%
Snow per year: 35.9"

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Frost risk by date in Walnut

Half of springs at Walnut, IL see their last 32°F night by April 24; only one in ten is past it by April 10, and one in ten still has one after May 9. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 4 20%, and after May 9 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 54% of the 158 Illinois stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 14 in half of years, as early as September 30 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 10 days later, around October 24; in spring the one-in-ten date for 28°F is April 29, 10 days before the 32°F one. The freeze-free season lasts 172 days in a typical year, shorter than at 82% of the 158 Illinois stations; it reaches 191 days one year in ten and falls short of 152 one year in ten. On average 136 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 9 days longer, to about May 3, and return around October 4. Severe cold of 16°F or below comes every winter, usually between November 22 and March 14.

Spring: the chance of another night this cold after the date
Low	90%	80%	70%	60%	50%	40%	30%	20%	10%
36°F	Apr 20	Apr 24	Apr 28	Apr 30	May 3	May 6	May 10	May 14	May 20
32°F	Apr 10	Apr 15	Apr 18	Apr 21	Apr 24	Apr 27	Apr 30	May 4	May 9
28°F	Mar 31	Apr 4	Apr 7	Apr 9	Apr 12	Apr 15	Apr 18	Apr 22	Apr 29
24°F	Mar 17	Mar 23	Mar 29	Mar 31	Apr 3	Apr 5	Apr 8	Apr 12	Apr 18
20°F	Mar 8	Mar 12	Mar 17	Mar 20	Mar 24	Mar 27	Mar 31	Apr 2	Apr 6
16°F	Feb 28	Mar 4	Mar 8	Mar 11	Mar 14	Mar 17	Mar 20	Mar 24	Mar 30

Fall: the chance the first night this cold has come by the date
Low	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Sep 21	Sep 25	Sep 29	Oct 1	Oct 4	Oct 6	Oct 9	Oct 12	Oct 16
32°F	Sep 30	Oct 5	Oct 8	Oct 11	Oct 14	Oct 16	Oct 19	Oct 22	Oct 27
28°F	Oct 11	Oct 15	Oct 19	Oct 21	Oct 24	Oct 26	Oct 29	Nov 1	Nov 5
24°F	Oct 20	Oct 25	Oct 28	Oct 31	Nov 2	Nov 5	Nov 8	Nov 12	Nov 17
20°F	Nov 1	Nov 4	Nov 7	Nov 10	Nov 13	Nov 16	Nov 19	Nov 23	Nov 29
16°F	Nov 7	Nov 12	Nov 16	Nov 19	Nov 22	Nov 25	Nov 29	Dec 3	Dec 9

Freeze probabilities 1991–2020 at Walnut, IL, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.

Frost risk on any date in 61376 →Compare Walnut with another place →

Frost risk through the year in Walnut

Frost curve for Walnut, Illinois (Walnut, IL, NOAA 1991–2020): the chance of another 32°F night falls from 90% on April 10 to 50% on April 24 and 10% on May 9; the chance that the first fall one has come rises from 10% on September 30 to 50% on October 14 and 90% on October 27. — In Walnut, the spring curve drops under 10% on May 9 and the fall curve passes 10% on September 30, 144 days later; that gap is shorter than at 79% of the 158 Illinois stations with frost dates. The spring risk falls from 90% to 10% over 29 days (April 10 to May 9) and the fall risk climbs from 10% to 90% over 27 days (September 30 to October 27): both ends of the season vary about as much. At Princeton, IL, 15 miles southeast, the same gap runs from May 7 to October 3, 5 days longer.

Chance of a frost after each planting date in Walnut
Planted on	Another 32°F night	28°F night
Apr 10	over 90%	57%
Apr 17	73%	33%
Apr 2450% date	50%	17%
May 1	28%	under 10%
May 8	12%	under 10%
May 15	under 10%	under 10%

Weather by month in Walnut

July is the warmest month at Walnut, IL, averaging 83°F by day and 63°F at night; January is the coldest at 29°F and 13°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 28% of years.

Warmth for growing adds up to 3,113 growing degree days a year (base 50°F), fewer than at 78% of the 158 Illinois stations. 36% of them (1,107) have built up by the end of June, and July adds the most, 724. Precipitation totals 36.7 inches a year, most in June (4.9") and least in January (1.5"); May to September bring 56% of it.

Monthly normals 1991–2020 at Walnut, IL
Month	High °F	Low °F	Precip. in	32°F night	Nights ≤ 32°F	GDD 50°F
Jan	29	13	1.5	100%	30	0
Feb	34	17	1.7	100%	26	1
Mar	47	28	2.2	100%	22	22
Apr	61	39	3.4	99%	7	113
May	72	51	4.6	28%	<1	358
Jun	81	60	4.9	0%	0	614
Jul	83	63	3.9	0%	0	724
Aug	82	61	3.8	0%	0	660
Sep	76	53	3.4	11%	<1	438
Oct	63	41	3.0	94%	6	156
Nov	48	30	2.3	100%	18	25
Dec	35	19	2.0	100%	28	2

Monthly normals 1991–2020 at Walnut, IL (671 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.

Compared with the next station

The nearest other station, Princeton, IL, 15 miles southeast of Walnut, has a last frost 2 days earlier (April 22), a first frost 3 days later (October 17), a season 5 days longer.

Frost dates for 61356 (Princeton) →

When it snows in Walnut, Illinois

The first measurable snow (0.1 inch or more) in Walnut usually arrives around December 1, and the last of the season around March 16. Those are the middle dates across the winters of 1991–2020 at Walnut, IL, 0.9 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 39 days after the last snow.

Planting calendar for 61376

What to do and when, from the 50% frost dates for Walnut, Illinois
When	What to do
February 13 – February 27	Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out.
February 27 – March 13	Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early.
March 27 – April 10	Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil.
April 24 onward	Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast.
by July 22	Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops.
by September 30	Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation.
October 14 onward	Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter.

The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.

Where these figures come from

ZIP 61376 is under a mile from Walnut, IL, which stands at 671 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 61376 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.

Frost dates across Illinois →

Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.

Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.