U.S. Frost Dates by Weather Station

NOAA station USW00014806 · Illinois

Frost Dates for Rantoul, IL

NOAA weather station Rantoul (USW00014806), Illinois · elevation 740 ft (226 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 6only 1 spring in 10 still has a frost later
  • Typical last frostApril 2150% chance of a frost after it
  • Typical first fall frostOctober 1850% chance of a frost before it
  • Frost-free season179 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Rantoul, ILSpring: a frost after April 7 in 9 years out of 10, after April 21 in half of the years, after May 6 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 18 in half of the years, before October 31 in 9 years out of 10. Typical frost-free season: 179 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 21First frost ~Oct 18Frost season at Rantoul, ILSpring: a frost after April 7 in 9 years out of 10, after April 21 in half of the years, after May 6 in 1 year out of 10. Fall: the first frost comes before October 5 in 1 year out of 10, before October 18 in half of the years, before October 31 in 9 years out of 10. Typical frost-free season: 179 days.JFMAMJJASONDLast frost ~Apr 21First frost ~Oct 18
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 6October 5
50% (typical)April 21October 18
90% (likely)April 7October 31
Frost-free season (32°F, 50% chance)
179 days
Hard frost (28°F), last in spring, 50% chance after
April 10
Hard frost (28°F), first in fall, 50% chance before
October 29

The last 15 years (2006–2020 normals)

Typical last frost April 20 (1 day earlier than the 30-year normal), typical first fall frost October 21 (3 days later). Frost-free season 183 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 Rantoul: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 6, 20% May 1, 30% April 27, 40% April 24, 50% April 21, 60% April 18, 70% April 15, 80% April 11, 90% April 7. Observed last spring frost in recent years: 2021 April 22, 2022 April 26, 2023 April 26.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 6Apr 21Apr 72021: April 222022: April 262023: April 26Fall at Rantoul: chance of a frost before this dateFall, chance of a frost before the date: 10% October 5, 20% October 10, 30% October 12, 40% October 15, 50% October 18, 60% October 21, 70% October 24, 80% October 27, 90% October 31. Observed first fall frost in recent years: 2021 October 31, 2022 October 7, 2023 October 30.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 5Oct 18Oct 312021: October 312022: October 72023: October 30
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 22October 31
2022April 26October 7
2023April 26October 30
2024no datano data
2025no datano data
2026no dataseason not over yet

What these dates mean

May 6 is the cautious spring date in Rantoul, carrying a 10 % chance of a light frost later, and it marks the point when a gardener can plan to set out tender crops with low frost risk. The 50 % spring median, April 21, and the 50 % fall median, October 18, each represent an even-odds moment for a light frost; they are not frost dates but indicate the midpoint of the probability curve. In the fall, October 5 is the cautious date, with only a 10 % chance that a light frost has already arrived, guiding the timing to finish harvesting tender crops.

The hard-frost median dates are April 10 in spring and October 29 in fall, and a hard frost at 28 °F can damage plants more severely than a light frost at 32 °F, so the lower temperature threshold is the more critical 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 6" 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 5" 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 Rantoul, ILNumbered nearest stations: 1 — Champaign, IL — 16 mi; 2 — Hoopeston, IL — 27 mi; 3 — Danville, IL — 30 mi; 4 — Tuscola, IL — 36 mi; 5 — Perrysville, IN — 38 mi.ILIN25 mi · 40 km1. Champaign, IL — 16 mi12. Hoopeston, IL — 27 mi23. Danville, IL — 30 mi34. Tuscola, IL — 36 mi45. Perrysville, IN — 38 mi5
  1. Champaign, IL 16 mi (26 km)
  2. Hoopeston, IL 27 mi (44 km)
  3. Danville, IL 30 mi (48 km)
  4. Tuscola, IL 36 mi (59 km)
  5. Perrysville, IN 38 mi (61 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: 40.3131, -88.1594.