U.S. Frost Dates by Weather Station

NOAA station USC00111436 · Illinois

Frost Dates for Charleston, IL

NOAA weather station Charleston (USC00111436), Illinois · elevation 700 ft (213 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 3only 1 spring in 10 still has a frost later
  • Typical last frostApril 1550% chance of a frost after it
  • Typical first fall frostOctober 2350% chance of a frost before it
  • Frost-free season187 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Charleston, ILSpring: a frost after April 1 in 9 years out of 10, after April 15 in half of the years, after May 3 in 1 year out of 10. Fall: the first frost comes before October 9 in 1 year out of 10, before October 23 in half of the years, before November 4 in 9 years out of 10. Typical frost-free season: 187 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 15First frost ~Oct 23Frost season at Charleston, ILSpring: a frost after April 1 in 9 years out of 10, after April 15 in half of the years, after May 3 in 1 year out of 10. Fall: the first frost comes before October 9 in 1 year out of 10, before October 23 in half of the years, before November 4 in 9 years out of 10. Typical frost-free season: 187 days.JFMAMJJASONDLast frost ~Apr 15First frost ~Oct 23
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 3October 9
50% (typical)April 15October 23
90% (likely)April 1November 4
Frost-free season (32°F, 50% chance)
187 days
Hard frost (28°F), last in spring, 50% chance after
April 3
Hard frost (28°F), first in fall, 50% chance before
November 2

The last 15 years (2006–2020 normals)

Typical last frost April 17 (2 days later than the 30-year normal), typical first fall frost October 23. Frost-free season 190 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 Charleston: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 3, 20% April 26, 30% April 22, 40% April 18, 50% April 15, 60% April 12, 70% April 9, 80% April 6, 90% April 1. Observed last spring frost in recent years: 2021 April 21, 2022 April 19, 2023 April 24, 2024 April 21, 2025 April 12, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 3Apr 15Apr 12021: April 212022: April 192023: April 242024: April 212025: April 122026: May 3Fall at Charleston: chance of a frost before this dateFall, chance of a frost before the date: 10% October 9, 20% October 13, 30% October 17, 40% October 20, 50% October 23, 60% October 25, 70% October 28, 80% October 31, 90% November 4. Observed first fall frost in recent years: 2021 November 3, 2022 October 9, 2023 October 12, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 9Oct 23Nov 42021: November 32022: October 92023: October 122024: October 162025: 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
2021April 21November 3
2022April 19October 9
2023April 24October 12
2024April 21October 16
2025April 12October 24
2026May 3season not over yet

What these dates mean

The 187 days between the 32°F 50% dates in Charleston—April 15 and October 23—define the window when statistically half of the recorded years have experienced a light frost before the end and half after the start. For a gardener this median period marks the span in which tender crops generally avoid a light frost, while still acknowledging that a frost could occur on either side of those dates.

A cautious planting schedule uses the May 3 date, which carries only a 10 % chance of a light frost later, for setting out tender crops in spring, and the October 9 date, also with a 10 % chance of a light frost earlier, for finishing harvest in fall. The hard-frost 50% dates are April 3 and November 2, and a hard frost at 28 °F can damage plants that would survive a light frost at 32 °F, making it a more severe threat.

How to read the probabilities

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

  • Spring: "10% after May 3" 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 9" 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 Charleston, ILNumbered nearest stations: 1 — Tuscola, IL — 23 mi; 2 — Windsor, IL — 23 mi; 3 — near Paris, IL — 28 mi; 4 — Effingham, IL — 35 mi; 5 — Champaign, IL — 42 mi.ILIN25 mi · 40 km1. Tuscola, IL — 23 mi12. Windsor, IL — 23 mi23. near Paris, IL — 28 mi34. Effingham, IL — 35 mi45. Champaign, IL — 42 mi5
  1. Tuscola, IL 23 mi (37 km)
  2. Windsor, IL 23 mi (37 km)
  3. near Paris, IL 28 mi (46 km)
  4. Effingham, IL 35 mi (56 km)
  5. Champaign, IL 42 mi (68 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: 39.4761, -88.1653.