U.S. Frost Dates by Weather Station

NOAA station USC00119354 · Illinois

Frost Dates for Windsor, IL

NOAA weather station Windsor (USC00119354), Illinois · elevation 690 ft (210 m) · hardiness zone 6b*

  • Lower-risk planting dateafter April 30only 1 spring in 10 still has a frost later
  • Typical last frostApril 1650% chance of a frost after it
  • Typical first fall frostOctober 2250% chance of a frost before it
  • Frost-free season187 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Windsor, ILSpring: a frost after April 3 in 9 years out of 10, after April 16 in half of the years, after April 30 in 1 year out of 10. Fall: the first frost comes before October 8 in 1 year out of 10, before October 22 in half of the years, before November 2 in 9 years out of 10. Typical frost-free season: 187 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 16First frost ~Oct 22Frost season at Windsor, ILSpring: a frost after April 3 in 9 years out of 10, after April 16 in half of the years, after April 30 in 1 year out of 10. Fall: the first frost comes before October 8 in 1 year out of 10, before October 22 in half of the years, before November 2 in 9 years out of 10. Typical frost-free season: 187 days.JFMAMJJASONDLast frost ~Apr 16First frost ~Oct 22
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 30October 8
50% (typical)April 16October 22
90% (likely)April 3November 2
Frost-free season (32°F, 50% chance)
187 days
Hard frost (28°F), last in spring, 50% chance after
April 5
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 14 (2 days earlier than the 30-year normal), typical first fall frost October 26 (4 days later). Frost-free season 192 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 Windsor: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 30, 20% April 25, 30% April 22, 40% April 19, 50% April 16, 60% April 13, 70% April 10, 80% April 7, 90% April 3. Observed last spring frost in recent years: 2022 April 20, 2023 April 26, 2024 April 6, 2025 April 12, 2026 March 29.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 30Apr 16Apr 32022: April 202023: April 262024: April 62025: April 122026: March 29Fall at Windsor: chance of a frost before this dateFall, chance of a frost before the date: 10% October 8, 20% October 14, 30% October 17, 40% October 20, 50% October 22, 60% October 25, 70% October 27, 80% October 30, 90% November 2. Observed first fall frost in recent years: 2021 November 3, 2022 October 18, 2023 October 31, 2024 October 17, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 8Oct 22Nov 22021: November 32022: October 182023: October 312024: October 172025: November 2
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
2021incomplete recordNovember 3
2022April 20October 18
2023April 26October 31
2024April 6October 17
2025April 12November 2
2026March 29season not over yet

What these dates mean

The early spring gamble is setting out tender crops on April 3, when a frost later in the season is still a 90 % chance. Waiting until the cautious date of April 30 lowers that risk to only a 10 % chance.

For a balanced plan the 50 % light-frost dates—April 16 in spring and October 22 in fall—mark the point where frost is equally likely to occur later (spring) or earlier (fall). The cautious fall date to finish harvesting tender crops is October 8, which carries just a 10 % chance of a frost arriving earlier. The interval between the two 32°F 50 % dates spans 187 days, based on 29 years of record.

Hard frosts at 28 °F are more damaging than light frosts at 32 °F, and the 50 % hard-frost dates are April 5 and November 1.

How to read the probabilities

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

  • Spring: "10% after April 30" 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 8" 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 Windsor, ILNumbered nearest stations: 1 — Effingham, IL — 23 mi; 2 — Charleston, IL — 23 mi; 3 — Tuscola, IL — 29 mi; 4 — Ramsey, IL — 34 mi; 5 — Champaign, IL — 48 mi.ILIN25 mi · 40 km1. Effingham, IL — 23 mi12. Charleston, IL — 23 mi23. Tuscola, IL — 29 mi34. Ramsey, IL — 34 mi45. Champaign, IL — 48 mi5
  1. Effingham, IL 23 mi (37 km)
  2. Charleston, IL 23 mi (37 km)
  3. Tuscola, IL 29 mi (47 km)
  4. Ramsey, IL 34 mi (55 km)
  5. Champaign, IL 48 mi (77 km)

Sources

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

Station coordinates: 39.4458, -88.5961.