Frost dates for Grand Chain Dam, Illinois
Half of years have their last spring frost by April 3, but 1 year in 10 still frosts after April 21.
A frost date is really a percentile from 30 years of records at a nearby weather station: in about half of years a frost still comes after the median date. Both numbers are below, so you can choose the risk yourself.
The odds
Last spring frost
How often a frost still comes on or after each date.
- 1 year in 10
- April 21
- 1 year in 5
- April 14
- 3 years in 10
- April 9
- 2 years in 5
- April 6
- Half of years (the median)
- April 3
First fall freeze
How often the first freeze comes on or before each date.
- 1 year in 10
- October 23
- 1 year in 5
- October 27
- 3 years in 10
- October 31
- 2 years in 5
- November 2
- Half of years (the median)
- November 5
- Growing season
- about 216 days
- Hardiness zone nearby
- 7a
- Summer days
- a usual high of about 31 °C88 °F
- Lettuce and spinach run to seed
- May to September, in hot, long days (how we know)
Summer and rain
A growing garden needs about 25 mm1 in of water a week, rain and watering together. Here is what a normal month brings.
Month by month
- January
- high ~6 °C43 °F · low ~-3 °C26 °F · rain ~107 mm4.2 in
- February
- high ~9 °C48 °F · low ~-1 °C30 °F · rain ~98 mm3.9 in
- March
- high ~14 °C57 °F · low ~3 °C37 °F · rain ~121 mm4.8 in
- April
- high ~20 °C68 °F · low ~8 °C47 °F · rain ~131 mm5.1 in
- May
- high ~25 °C77 °F · low ~14 °C56 °F · rain ~125 mm4.9 in
- June
- high ~30 °C85 °F · low ~18 °C65 °F · rain ~105 mm4.1 in
- July
- high ~32 °C89 °F · low ~20 °C69 °F · rain ~83 mm3.3 in
- August
- high ~31 °C89 °F · low ~20 °C67 °F · rain ~77 mm3 in
- September
- high ~28 °C83 °F · low ~16 °C60 °F · rain ~85 mm3.4 in
- October
- high ~22 °C71 °F · low ~9 °C48 °F · rain ~103 mm4 in
- November
- high ~14 °C58 °F · low ~4 °C39 °F · rain ~112 mm4.4 in
- December
- high ~8 °C47 °F · low ~-1 °C31 °F · rain ~108 mm4.2 in
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, the Grand Chain Dam station (listed by NOAA as Grand Chain Dam, USC00113580), at 37.20, -89.04. These are that station’s own records, unshifted. The further your garden is from it, the less exactly they describe your ground. The planner finds the nearest station to your garden and lowers its confidence with distance, so no number is presented as if it were measured in your garden.
Cold air also pools in low ground on the clear, still nights when frost happens, so a hollow can freeze while a slope a few hundred feet away does not. No table can know that about your garden. A few seasons of your own logged frosts can.
ZIP codes nearest this station
42022, 42024, 42053, 42056, 62906, 62908, 62912, 62914, 62923, 62926, 62941, 62953…
+9 moreShow fewer
62956, 62961, 62963, 62964, 62970, 62976, 62988, 62992, 62996.
Nearby stations
The nearest stations and how their last-frost dates compare. Together they show how frost varies across your area.
- Carbondale Southern Il Airport, IL, last frost by April 9
- Harrisburg, IL, last frost by April 7
Other stations in Illinois.
- Belleville SIU Rsch, IL, last frost by April 12
- Hillsboro, IL, last frost by April 13
- Carlinville, IL, last frost by April 14
- Decatur Airport, IL, last frost by April 16
- Springfield #2, IL, last frost by April 15
- Danville, IL, last frost by April 21
- Rantoul, IL, last frost by April 21
- Congerville 2 NW, IL, last frost by April 21
When do I plant? · Where the dates come from
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