U.S. Frost Dates by Weather Station

NOAA station USC00116616 · Illinois

Frost Dates for Park Forest, IL

NOAA weather station Park Forest (USC00116616), Illinois · elevation 710 ft (216 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 2350% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season179 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Park Forest, ILSpring: a frost after April 9 in 9 years out of 10, after April 23 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 20 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 179 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 23First frost ~Oct 20Frost season at Park Forest, ILSpring: a frost after April 9 in 9 years out of 10, after April 23 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 20 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 179 days.JFMAMJJASONDLast frost ~Apr 23First frost ~Oct 20
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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 11October 6
50% (typical)April 23October 20
90% (likely)April 9November 1
Frost-free season (32°F, 50% chance)
179 days
Hard frost (28°F), last in spring, 50% chance after
April 12
Hard frost (28°F), first in fall, 50% chance before
October 30

The last 15 years (2006–2020 normals)

Typical last frost April 21 (2 days earlier than the 30-year normal), typical first fall frost October 25 (5 days later). Frost-free season 184 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 at Park Forest: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 11, 20% May 5, 30% April 30, 40% April 27, 50% April 23, 60% April 20, 70% April 18, 80% April 14, 90% April 9. Observed last spring frost in recent years: 2021 May 9, 2022 April 28, 2023 April 27, 2024 April 26, 2025 April 13, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 11Apr 23Apr 92021: May 92022: April 282023: April 272024: April 262025: April 132026: May 3Fall at Park Forest: chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 12, 30% October 15, 40% October 18, 50% October 20, 60% October 23, 70% October 25, 80% October 28, 90% November 1. Observed first fall frost in recent years: 2021 November 2, 2022 October 9, 2023 October 31, 2024 October 18, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 20Nov 12021: November 22022: October 92023: October 312024: October 182025: October 24
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
2021May 9November 2
2022April 28October 9
2023April 27October 31
2024April 26October 18
2025April 13October 24
2026May 3season not over yet

What these dates mean

Planting tender crops on April 9 in Park Forest is a gamble, as a 90% chance of a light frost later than that date remains. Gardeners who prefer a lower risk wait until May 11, which carries only a 10% chance of a frost after planting.

The median light-frost dates are April 23 in spring and October 20 in fall; each marks the point at which a light frost is equally likely to have occurred or not. For a cautious fall schedule, harvesting tender crops by October 6 limits the chance of an early frost to 10%, whereas waiting until November 1 would be a gamble with a 90% chance of a frost already having arrived.

Hard frost at 28 °F, with median dates of April 12 and October 30, matters more because it can cause more severe damage than a 32 °F light 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 11" 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 6" 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 Park Forest, ILNumbered nearest stations: 1 — near Chicago, IL — 17 mi; 2 — Lowell, IN — 21 mi; 3 — near Joliet, IL — 22 mi; 4 — near Kankakee, IL — 27 mi; 5 — Indiana Dunes NL, IN — 32 mi.INMI25 mi · 40 km1. near Chicago, IL — 17 mi12. Lowell, IN — 21 mi23. near Joliet, IL — 22 mi34. near Kankakee, IL — 27 mi45. Indiana Dunes NL, IN — 32 mi5
  1. near Chicago, IL 17 mi (28 km)
  2. Lowell, IN 21 mi (34 km)
  3. near Joliet, IL 22 mi (35 km)
  4. near Kankakee, IL 27 mi (44 km)
  5. Indiana Dunes NL, IN 32 mi (52 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: 41.4947, -87.6803.