U.S. Frost Dates by Weather Station

NOAA station USC00110598 · Illinois

Frost Dates for Bentley, IL

NOAA weather station Bentley (USC00110598), Illinois · elevation 650 ft (198 m) · hardiness zone 6a*

  • Lower-risk planting dateafter April 30only 1 spring in 10 still has a frost later
  • Typical last frostApril 1350% chance of a frost after it
  • Typical first fall frostOctober 2250% chance of a frost before it
  • Frost-free season191 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Bentley, ILSpring: a frost after March 30 in 9 years out of 10, after April 13 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 4 in 9 years out of 10. Typical frost-free season: 191 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 13First frost ~Oct 22Frost season at Bentley, ILSpring: a frost after March 30 in 9 years out of 10, after April 13 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 4 in 9 years out of 10. Typical frost-free season: 191 days.JFMAMJJASONDLast frost ~Apr 13First 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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)April 30October 8
50% (typical)April 13October 22
90% (likely)March 30November 4
Frost-free season (32°F, 50% chance)
191 days
Hard frost (28°F), last in spring, 50% chance after
April 3
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 15 (2 days later than the 30-year normal), typical first fall frost October 24 (2 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 Bentley: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 30, 20% April 24, 30% April 20, 40% April 16, 50% April 13, 60% April 10, 70% April 8, 80% April 4, 90% March 30. Observed last spring frost in recent years: 2021 April 23, 2022 April 27, 2023 April 24, 2024 April 6, 2025 April 9, 2026 March 29.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 30Apr 13Mar 302021: April 232022: April 272023: April 242024: April 62025: April 92026: March 29Fall at Bentley: 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 4. Observed first fall frost in recent years: 2021 November 2, 2022 October 18, 2023 October 30, 2024 October 17, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 8Oct 22Nov 42021: November 22022: October 182023: October 302024: 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
2021April 23November 2
2022April 27October 18
2023April 24October 30
2024April 6October 17
2025April 9November 2
2026March 29season not over yet

What these dates mean

The 191 days between the 32 °F 50% dates in Bentley—April 13 and October 22—frame the period when light frosts are less probable. The 50% date is April 13, a 50% chance of a light frost later than this date, and the 50% date is October 22, a 50% chance of a light frost earlier than this date. The hard-frost 50% dates are April 3 and November 1.

For a cautious spring plan the 10% chance date, April 30, is used as the latest moment to set out tender crops, while the gamble date, March 30 with a 90% chance, should be avoided. In the fall the cautious date is October 8, carrying only a 10% chance of a frost having arrived, and the gamble date is November 4 with a 90% chance. A hard frost at 28 °F can damage plant tissue that may 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 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 Bentley, ILNumbered nearest stations: 1 — near Keokuk, IA — 14 mi; 2 — Fort Madison, IA — 22 mi; 3 — near Canton, MO — 25 mi; 4 — Quincy, IL — 28 mi; 5 — near Burlington, IA — 30 mi.ILMOIA25 mi · 40 km1. near Keokuk, IA — 14 mi12. Fort Madison, IA — 22 mi23. near Canton, MO — 25 mi34. Quincy, IL — 28 mi45. near Burlington, IA — 30 mi5
  1. near Keokuk, IA 14 mi (23 km)
  2. Fort Madison, IA 22 mi (36 km)
  3. near Canton, MO 25 mi (41 km)
  4. Quincy, IL 28 mi (46 km)
  5. near Burlington, IA 30 mi (48 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: 40.3444, -91.1125.