Frost dates for Chicago Botanic Garden, Illinois
Half of years have their last spring frost by April 26, but 1 year in 10 still frosts after May 11.
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
- May 11
- 1 year in 5
- May 6
- 3 years in 10
- May 2
- 2 years in 5
- April 30
- Half of years (the median)
- April 26
First fall freeze
How often the first freeze comes on or before each date.
- 1 year in 10
- October 5
- 1 year in 5
- October 11
- 3 years in 10
- October 14
- 2 years in 5
- October 18
- Half of years (the median)
- October 21
- Growing season
- about 176 days
- Hardiness zones nearby
- 5b, 6a
- Summer days
- a usual high of about 27 °C81 °F
- Lettuce and spinach run to seed
- June 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 ~0 °C32 °F · low ~-9 °C16 °F · rain ~53 mm2.1 in
- February
- high ~2 °C36 °F · low ~-7 °C19 °F · rain ~50 mm2 in
- March
- high ~8 °C46 °F · low ~-2 °C28 °F · rain ~57 mm2.3 in
- April
- high ~14 °C57 °F · low ~3 °C38 °F · rain ~102 mm4 in
- May
- high ~20 °C68 °F · low ~9 °C48 °F · rain ~123 mm4.8 in
- June
- high ~26 °C78 °F · low ~14 °C57 °F · rain ~110 mm4.3 in
- July
- high ~29 °C83 °F · low ~17 °C63 °F · rain ~95 mm3.7 in
- August
- high ~28 °C82 °F · low ~17 °C62 °F · rain ~106 mm4.2 in
- September
- high ~24 °C75 °F · low ~13 °C55 °F · rain ~90 mm3.6 in
- October
- high ~17 °C63 °F · low ~6 °C43 °F · rain ~91 mm3.6 in
- November
- high ~9 °C49 °F · low ~0 °C33 °F · rain ~67 mm2.6 in
- December
- high ~3 °C38 °F · low ~-5 °C22 °F · rain ~59 mm2.3 in
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, the Chicago Botanic Garden station (listed by NOAA as Chicago Botanic Garden, USC00111497), at 42.14, -87.79. 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
60004, 60005, 60007, 60008, 60015, 60016, 60018, 60022, 60025, 60026, 60029, 60035…
+35 moreShow fewer
60040, 60043, 60044, 60045, 60048, 60053, 60056, 60061, 60062, 60064, 60067, 60068, 60069, 60070, 60074, 60076, 60077, 60088, 60089, 60090, 60091, 60093, 60173, 60176, 60195, 60201, 60202, 60203, 60626, 60631, 60645, 60646, 60656, 60712, 60714.
Nearby stations
The nearest stations and how their last-frost dates compare. Together they show how frost varies across your area.
- Chicago Northerly Island, IL, last frost by April 10
- Chicago Midway Airport, IL, last frost by April 11
- Mc Henry WG Stratton L&D, IL, last frost by May 1
- Lisle-Morton Arboretum, IL, last frost by April 28
- Aurora, IL, last frost by April 19
- Racine Batten Airport, WI, last frost by April 24
Other stations in Illinois.
- Park Forest, IL, last frost by April 23
- Rockford Greater Rockford Airport, IL, last frost by April 24
- Hennepin Wtr Trmt Plt, IL, last frost by April 24
- Rantoul, IL, last frost by April 21
- Congerville 2 NW, IL, last frost by April 21
- Danville, IL, last frost by April 21
- Peoria Greater Peoria Airport, IL, last frost by April 16
- Aledo, IL, last frost by April 22
When do I plant? · Where the dates come from
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