U.S. Frost Dates by Weather Station

NOAA station USC00116200 · Illinois

Frost Dates for Normal, IL

NOAA weather station Normal 4 NE (USC00116200), Illinois · elevation 790 ft (241 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 2550% chance of a frost after it
  • Typical first fall frostOctober 1650% chance of a frost before it
  • Frost-free season172 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Normal, ILSpring: a frost after April 11 in 9 years out of 10, after April 25 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 2 in 1 year out of 10, before October 16 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 172 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 25First frost ~Oct 16Frost season at Normal, ILSpring: a frost after April 11 in 9 years out of 10, after April 25 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before October 2 in 1 year out of 10, before October 16 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 172 days.JFMAMJJASONDLast frost ~Apr 25First frost ~Oct 16
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)May 11October 2
50% (typical)April 25October 16
90% (likely)April 11October 29
Frost-free season (32°F, 50% chance)
172 days
Hard frost (28°F), last in spring, 50% chance after
April 14
Hard frost (28°F), first in fall, 50% chance before
October 27

The last 15 years (2006–2020 normals)

Typical last frost April 26 (1 day later than the 30-year normal), typical first fall frost October 21 (5 days later). Frost-free season 177 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 Normal: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 11, 20% May 5, 30% May 1, 40% April 29, 50% April 25, 60% April 21, 70% April 18, 80% April 15, 90% April 11. Observed last spring frost in recent years: 2021 May 14, 2022 April 28, 2024 April 26, 2025 April 17, 2026 April 21.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 11Apr 25Apr 112021: May 142022: April 282024: April 262025: April 172026: April 21Fall at Normal: chance of a frost before this dateFall, chance of a frost before the date: 10% October 2, 20% October 7, 30% October 11, 40% October 14, 50% October 16, 60% October 19, 70% October 22, 80% October 25, 90% October 29. Observed first fall frost in recent years: 2021 November 2, 2022 September 30, 2023 October 30, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 2Oct 16Oct 292021: November 22022: September 302023: October 302024: 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
2021May 14November 2
2022April 28September 30
2023incomplete recordOctober 30
2024April 26October 16
2025April 17October 24
2026April 21season not over yet

What these dates mean

May 11 is the cautious spring date in Normal, and it marks the point at which a gardener can set out tender crops with only a 10% chance of a light frost later. The earlier April 11 date carries a 90% chance of a frost and is therefore a gamble, while the median 50% date of April 25 represents a 50% chance of a light frost later than that date.

In the fall, October 2 is the cautious date for finishing harvest of tender crops, offering only a 10% chance that a light frost has arrived earlier. The median 50% date of October 16 represents a 50% chance of a frost earlier than that date. Hard frosts at 28°F are more damaging than light frosts at 32°F, and the median hard-frost dates of April 14 and October 27 highlight when temperatures can reach the more severe level.

How to read the probabilities

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

  • Spring: "10% after May 11" 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 2" 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 Normal, ILNumbered nearest stations: 1 — Chenoa, IL — 18 mi; 2 — Minonk, IL — 25 mi; 3 — Pontiac, IL — 28 mi; 4 — Lincoln, IL — 34 mi; 5 — Peoria, IL — 39 mi.IL25 mi · 40 km1. Chenoa, IL — 18 mi12. Minonk, IL — 25 mi23. Pontiac, IL — 28 mi34. Lincoln, IL — 34 mi45. Peoria, IL — 39 mi5
  1. Chenoa, IL 18 mi (29 km)
  2. Minonk, IL 25 mi (41 km)
  3. Pontiac, IL 28 mi (45 km)
  4. Lincoln, IL 34 mi (55 km)
  5. Peoria, IL 39 mi (63 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: 40.5492, -88.9497.