U.S. Frost Dates by Weather Station

NOAA station USC00114530 · Illinois

Frost Dates near Joliet, IL

NOAA weather station Joliet Brandon RD Dam (USC00114530), Illinois · elevation 543 ft (166 m) · hardiness zone 6a*

Joliet is the nearest town to the station (1.8 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 May 7only 1 spring in 10 still has a frost later
  • Typical last frostApril 1950% chance of a frost after it
  • Typical first fall frostOctober 2550% chance of a frost before it
  • Frost-free season188 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season near Joliet, ILSpring: a frost after April 3 in 9 years out of 10, after April 19 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before October 12 in 1 year out of 10, before October 25 in half of the years, before November 6 in 9 years out of 10. Typical frost-free season: 188 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 19First frost ~Oct 25Frost season near Joliet, ILSpring: a frost after April 3 in 9 years out of 10, after April 19 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before October 12 in 1 year out of 10, before October 25 in half of the years, before November 6 in 9 years out of 10. Typical frost-free season: 188 days.JFMAMJJASONDLast frost ~Apr 19First frost ~Oct 25
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.Today

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)May 7October 12
50% (typical)April 19October 25
90% (likely)April 3November 6
Frost-free season (32°F, 50% chance)
188 days
Hard frost (28°F), last in spring, 50% chance after
April 5
Hard frost (28°F), first in fall, 50% chance before
November 4

The last 15 years (2006–2020 normals)

Typical last frost April 19 (same as the 30-year normal), typical first fall frost October 24 (1 day earlier). Frost-free season 187 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 Joliet: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 7, 20% April 30, 30% April 26, 40% April 22, 50% April 19, 60% April 16, 70% April 12, 80% April 9, 90% April 3. Observed last spring frost in recent years: 2021 April 23, 2022 April 27, 2023 April 24, 2024 April 24, 2025 April 9, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 7Apr 19Apr 32021: April 232022: April 272023: April 242024: April 242025: April 92026: May 3Fall near Joliet: chance of a frost before this dateFall, chance of a frost before the date: 10% October 12, 20% October 17, 30% October 20, 40% October 23, 50% October 25, 60% October 27, 70% October 30, 80% November 1, 90% November 6. Observed first fall frost in recent years: 2021 November 2, 2022 October 19, 2023 October 12, 2024 October 28, 2025 October 25.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 12Oct 25Nov 62021: November 22022: October 192023: October 122024: October 282025: October 25
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 23November 2
2022April 27October 19
2023April 24October 12
2024April 24October 28
2025April 9October 25
2026May 3season not over yet

What these dates mean

The 188 days between the 50% dates in the Joliet area define the main growing window for tender crops. The 50% spring light-frost date is April 19 and the 50% fall light-frost date is October 25; each marks the point at which a light frost has an even chance of occurring. Hard-frost 50% dates are April 5 in spring and November 4 in fall, and a hard frost matters more than a light frost because 28 °F can damage plant tissues that survive 32 °F. In spring the cautious date for setting out tender crops is May 7, when only a 10 % chance of a later frost remains. In fall the cautious date to finish harvesting tender crops is October 12, also with a 10 % chance of an earlier frost.

How to read the probabilities

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

  • Spring: "10% after May 7" 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 12" 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 Joliet, ILNumbered nearest stations: 1 — Aurora, IL — 22 mi; 2 — Park Forest, IL — 22 mi; 3 — near Chicago, IL — 23 mi; 4 — near Kankakee, IL — 28 mi; 5 — Dwight, IL — 32 mi.ILINMI25 mi · 40 km1. Aurora, IL — 22 mi12. Park Forest, IL — 22 mi23. near Chicago, IL — 23 mi34. near Kankakee, IL — 28 mi45. Dwight, IL — 32 mi5
  1. Aurora, IL 22 mi (35 km)
  2. Park Forest, IL 22 mi (35 km)
  3. near Chicago, IL 23 mi (38 km)
  4. near Kankakee, IL 28 mi (45 km)
  5. Dwight, IL 32 mi (51 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: 41.5033, -88.1033.