U.S. Frost Dates by Weather Station

NOAA station USC00115712 · Illinois

Frost Dates for Minonk, IL

NOAA weather station Minonk (USC00115712), Illinois · elevation 750 ft (229 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 10only 1 spring in 10 still has a frost later
  • Typical last frostApril 2650% chance of a frost after it
  • Typical first fall frostOctober 1750% chance of a frost before it
  • Frost-free season173 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Minonk, ILSpring: a frost after April 11 in 9 years out of 10, after April 26 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 17 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 173 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 26First frost ~Oct 17Frost season at Minonk, ILSpring: a frost after April 11 in 9 years out of 10, after April 26 in half of the years, after May 10 in 1 year out of 10. Fall: the first frost comes before October 1 in 1 year out of 10, before October 17 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 173 days.JFMAMJJASONDLast frost ~Apr 26First frost ~Oct 17
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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 10October 1
50% (typical)April 26October 17
90% (likely)April 11October 29
Frost-free season (32°F, 50% chance)
173 days
Hard frost (28°F), last in spring, 50% chance after
April 15
Hard frost (28°F), first in fall, 50% chance before
October 28

The last 15 years (2006–2020 normals)

Typical last frost April 25 (1 day earlier than the 30-year normal), typical first fall frost October 19 (2 days later). Frost-free season 176 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 Minonk: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 10, 20% May 5, 30% May 1, 40% April 29, 50% April 26, 60% April 23, 70% April 20, 80% April 16, 90% April 11. Observed last spring frost in recent years: 2021 May 12, 2022 April 27, 2023 April 27, 2024 April 25, 2025 April 16, 2026 April 20.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 10Apr 26Apr 112021: May 122022: April 272023: April 272024: April 252025: April 162026: April 20Fall at Minonk: chance of a frost before this dateFall, chance of a frost before the date: 10% October 1, 20% October 7, 30% October 12, 40% October 14, 50% October 17, 60% October 20, 70% October 22, 80% October 25, 90% October 29. Observed first fall frost in recent years: 2021 November 1, 2022 October 8, 2023 October 29, 2024 October 15, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 1Oct 17Oct 292021: November 12022: October 82023: October 292024: October 152025: October 23
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 12November 1
2022April 27October 8
2023April 27October 29
2024April 25October 15
2025April 16October 23
2026April 20season not over yet

What these dates mean

October 1 marks the cautious fall date for finishing the harvest of tender crops in Minonk, as there is only a 10 % chance that a light frost has arrived earlier. For a gardener, the 50 % light-frost dates—April 26 in spring and October 17 in fall—indicate the point where a frost is equally likely to occur later (spring) or earlier (fall); they do not represent a guaranteed frost.

A cautious planting plan uses the May 10 light-frost date, which carries a 10 % chance of frost later, for setting out tender crops in spring, and relies on the October 1 date for ending the season in fall. The hard-frost 50 % dates are April 15 and October 28, and a hard frost at 28 °F can damage plants that survive a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after May 10" 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 1" 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 Minonk, ILNumbered nearest stations: 1 — Chenoa, IL — 20 mi; 2 — Pontiac, IL — 21 mi; 3 — Normal, IL — 25 mi; 4 — Ottawa, IL — 29 mi; 5 — Peru, IL — 30 mi.IN25 mi · 40 km1. Chenoa, IL — 20 mi12. Pontiac, IL — 21 mi23. Normal, IL — 25 mi34. Ottawa, IL — 29 mi45. Peru, IL — 30 mi5
  1. Chenoa, IL 20 mi (33 km)
  2. Pontiac, IL 21 mi (34 km)
  3. Normal, IL 25 mi (41 km)
  4. Ottawa, IL 29 mi (47 km)
  5. Peru, IL 30 mi (49 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 40.9125, -89.0339.