U.S. Frost Dates by Weather Station

NOAA station USC00111577 · Illinois

Frost Dates near Chicago, IL

NOAA weather station Chicago Midway Airport 3 SW (USC00111577), Illinois · elevation 620 ft (189 m) · hardiness zone 6a*

Chicago is the nearest town to the station (10.2 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter April 26only 1 spring in 10 still has a frost later
  • Typical last frostApril 1050% chance of a frost after it
  • Typical first fall frostNovember 150% chance of a frost before it
  • Frost-free season203 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season near Chicago, ILSpring: a frost after March 30 in 9 years out of 10, after April 10 in half of the years, after April 26 in 1 year out of 10. Fall: the first frost comes before October 21 in 1 year out of 10, before November 1 in half of the years, before November 16 in 9 years out of 10. Typical frost-free season: 203 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 10First frost ~Nov 1Frost season near Chicago, ILSpring: a frost after March 30 in 9 years out of 10, after April 10 in half of the years, after April 26 in 1 year out of 10. Fall: the first frost comes before October 21 in 1 year out of 10, before November 1 in half of the years, before November 16 in 9 years out of 10. Typical frost-free season: 203 days.JFMAMJJASONDLast frost ~Apr 10First frost ~Nov 1
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 26October 21
50% (typical)April 10November 1
90% (likely)March 30November 16
Frost-free season (32°F, 50% chance)
203 days
Hard frost (28°F), last in spring, 50% chance after
April 1
Hard frost (28°F), first in fall, 50% chance before
November 11

The last 15 years (2006–2020 normals)

Typical last frost April 12 (2 days later than the 30-year normal), typical first fall frost November 1. Frost-free season 202 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring near Chicago: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 26, 20% April 20, 30% April 17, 40% April 14, 50% April 10, 60% April 7, 70% April 5, 80% April 2, 90% March 30. Observed last spring frost in recent years: 2021 April 22, 2022 March 29, 2023 April 17, 2024 March 28, 2025 April 8, 2026 May 2.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 26Apr 10Mar 302021: April 222022: March 292023: April 172024: March 282025: April 82026: May 2Fall near Chicago: chance of a frost before this dateFall, chance of a frost before the date: 10% October 21, 20% October 25, 30% October 28, 40% October 30, 50% November 1, 60% November 3, 70% November 6, 80% November 10, 90% November 16. Observed first fall frost in recent years: 2021 November 2, 2022 November 13, 2023 October 30, 2024 November 21, 2025 November 9.Fall: first frostChance of a frost before this date10%50%90%Nov 1Oct 21Nov 1Nov 162021: November 22022: November 132023: October 302024: November 212025: November 9
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021April 22November 2
2022March 29November 13
2023April 17October 30
2024March 28November 21
2025April 8November 9
2026May 2season not over yet

What these dates mean

October 21 marks the cautious fall date for the Chicago area, when there is only a 10 % chance that a light frost has arrived and tender crops should be harvested by then. In spring the cautious date for setting out tender crops is April 26, which carries a 10 % chance of a later frost, while March 30 carries a 90 % chance and is a gamble.

The 50 % dates are April 10 for spring and November 1 for fall; each represents an even odds point for a light frost, so a gardener can expect about a fifty-fifty chance of frost occurring after April 10 or before November 1. These dates are not frost dates themselves but serve as reference points for risk assessment.

Hard frost at 28 °F is more damaging than a light frost at 32 °F because it can kill plant tissue that survives the milder temperature.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after April 26" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before October 21" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Chicago, ILNumbered nearest stations: 1 — Park Forest, IL — 17 mi; 2 — Chicago (O'Hare Airport), IL — 20 mi; 3 — near Joliet, IL — 23 mi; 4 — Aurora, IL — 28 mi; 5 — Chicago Botanic Garden, IL — 28 mi.ILINWIMI25 mi · 40 km1. Park Forest, IL — 17 mi12. Chicago (O'Hare Airport), IL — 20 mi23. near Joliet, IL — 23 mi34. Aurora, IL — 28 mi45. Chicago Botanic Garden, IL — 28 mi5
  1. Park Forest, IL 17 mi (28 km)
  2. Chicago (O'Hare Airport), IL 20 mi (31 km)
  3. near Joliet, IL 23 mi (38 km)
  4. Aurora, IL 28 mi (44 km)
  5. Chicago Botanic Garden, IL 28 mi (45 km)

Sources

* Hardiness zone 6a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.7372, -87.7775.