U.S. Frost Dates by Weather Station

NOAA station USW00013802 · Illinois

Frost Dates near Belleville, IL

NOAA weather station Belleville SIU Research (USW00013802), Illinois · elevation 450 ft (137 m) · hardiness zone 6b*

Belleville is the nearest town to the station (7.4 mi away) in GeoNames (CC BY 4.0). The dates below are measured at the station, not in the town itself.

  • Lower-risk planting dateafter April 28only 1 spring in 10 still has a frost later
  • Typical last frostApril 1250% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season189 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season near Belleville, ILSpring: a frost after March 28 in 9 years out of 10, after April 12 in half of the years, after April 28 in 1 year out of 10. Fall: the first frost comes before October 3 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: 189 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 12First frost ~Oct 20Frost season near Belleville, ILSpring: a frost after March 28 in 9 years out of 10, after April 12 in half of the years, after April 28 in 1 year out of 10. Fall: the first frost comes before October 3 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: 189 days.JFMAMJJASONDLast frost ~Apr 12First 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)April 28October 3
50% (typical)April 12October 20
90% (likely)March 28November 1
Frost-free season (32°F, 50% chance)
189 days
Hard frost (28°F), last in spring, 50% chance after
March 31
Hard frost (28°F), first in fall, 50% chance before
October 30

The last 15 years (2006–2020 normals)

Typical last frost April 10 (2 days earlier than the 30-year normal), typical first fall frost October 23 (3 days later). Frost-free season 195 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 near Belleville: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 28, 20% April 22, 30% April 19, 40% April 15, 50% April 12, 60% April 8, 70% April 5, 80% April 2, 90% March 28. Observed last spring frost in recent years: 2023 April 24, 2024 April 6, 2025 March 21, 2026 March 28.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 28Apr 12Mar 282023: April 242024: April 62025: March 212026: March 28Fall near Belleville: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 10, 30% October 14, 40% October 17, 50% October 20, 60% October 22, 70% October 25, 80% October 28, 90% November 1. Observed first fall frost in recent years: 2021 November 3, 2022 October 8, 2023 October 30, 2024 October 16, 2025 November 10.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 20Nov 12021: November 32022: October 82023: October 302024: October 162025: November 10
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
2022incomplete recordOctober 8
2023April 24October 30
2024April 6October 16
2025March 21November 10
2026March 28season not over yet

What these dates mean

Setting out tender crops on the early spring date, March 28, carries a 90% chance of a light frost later, so planting then is a gamble for growers in the Belleville area.

The median light-frost dates are April 12 in spring and October 20 in fall; each marks a 50% chance of a frost occurring after or before the date, respectively. Gardeners can use the cautious dates—April 28 for starting tender crops and October 3 for finishing them—because only a 10% chance of a frost exists beyond those points.

A hard frost, defined as 28 °F, can damage plants more severely than a light 32 °F frost, making the 50% hard-frost dates of March 31 and October 30 useful reference points for the risk of deeper freeze.

How to read the probabilities

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

  • Spring: "10% after April 28" 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 3" 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 Belleville, ILNumbered nearest stations: 1 — near Carlyle, IL — 27 mi; 2 — Nashville, IL — 29 mi; 3 — Festus, MO — 36 mi; 4 — St. Charles, MO — 38 mi; 5 — St. Louis (Spirit of St. Louis Airport), MO — 45 mi.ILMO25 mi · 40 km1. near Carlyle, IL — 27 mi12. Nashville, IL — 29 mi23. Festus, MO — 36 mi34. St. Charles, MO — 38 mi45. St. Louis (Spirit of St. Louis Airport), MO — 45 mi5
  1. near Carlyle, IL 27 mi (44 km)
  2. Nashville, IL 29 mi (47 km)
  3. Festus, MO 36 mi (58 km)
  4. St. Charles, MO 38 mi (62 km)
  5. St. Louis (Spirit of St. Louis Airport), MO 45 mi (72 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: 38.52, -89.8467.