U.S. Frost Dates by Weather Station

NOAA station USC00113384 · Illinois

Frost Dates for Geneseo, IL

NOAA weather station Geneseo (USC00113384), Illinois · elevation 639 ft (195 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 6only 1 spring in 10 still has a frost later
  • Typical last frostApril 2050% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season180 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Geneseo, ILSpring: a frost after April 6 in 9 years out of 10, after April 20 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 20 in half of the years, before October 31 in 9 years out of 10. Typical frost-free season: 180 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 20First frost ~Oct 20Frost season at Geneseo, ILSpring: a frost after April 6 in 9 years out of 10, after April 20 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 20 in half of the years, before October 31 in 9 years out of 10. Typical frost-free season: 180 days.JFMAMJJASONDLast frost ~Apr 20First 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 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 6October 5
50% (typical)April 20October 20
90% (likely)April 6October 31
Frost-free season (32°F, 50% chance)
180 days
Hard frost (28°F), last in spring, 50% chance after
April 9
Hard frost (28°F), first in fall, 50% chance before
October 30

The last 15 years (2006–2020 normals)

Typical last frost April 21 (1 day later than the 30-year normal), typical first fall frost October 21 (1 day later). Frost-free season 182 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 Geneseo: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 6, 20% May 1, 30% April 26, 40% April 23, 50% April 20, 60% April 17, 70% April 14, 80% April 10, 90% April 6. Observed last spring frost in recent years: 2021 April 22, 2022 April 27, 2023 April 26, 2024 April 21, 2025 April 8, 2026 April 20.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 6Apr 20Apr 62021: April 222022: April 272023: April 262024: April 212025: April 82026: April 20Fall at Geneseo: chance of a frost before this dateFall, chance of a frost before the date: 10% October 5, 20% October 11, 30% October 15, 40% October 18, 50% October 20, 60% October 22, 70% October 24, 80% October 27, 90% October 31. Observed first fall frost in recent years: 2021 October 23, 2022 October 14, 2023 October 30, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 5Oct 20Oct 312021: October 232022: October 142023: 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
2021April 22October 23
2022April 27October 14
2023April 26October 30
2024April 21October 16
2025April 8October 24
2026April 20season not over yet

What these dates mean

Planting tender crops on the early spring date of April 6 carries a 90% chance that a light frost will still occur later that season, making it a gamble. A more cautious approach uses the May 6 date, when only a 10% chance remains for a later light frost.

The 50% spring date is April 20, meaning there is a 50% chance of a light frost later than this date; the 50% fall date is October 20, meaning there is a 50% chance of a light frost earlier than this date. Hard-frost thresholds have the 50% dates of April 9 and October 30; a hard frost at 28°F can injure plants that would survive a 32°F light frost, so these dates are especially significant.

For the autumn harvest, the cautious fall date is October 5, the point at which only a 10% chance exists that a light frost has already arrived, while October 31 remains a gamble with a 90% chance of an earlier frost. The interval between the two 32°F 50% dates is 180 days, based on a 30-year record.

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 Geneseo, ILNumbered nearest stations: 1 — near Le Claire, IA — 16 mi; 2 — Kewanee, IL — 19 mi; 3 — near Moline, IL — 19 mi; 4 — Galva, IL — 20 mi; 5 — near Rock Island, IL — 22 mi.IA25 mi · 40 km1. near Le Claire, IA — 16 mi12. Kewanee, IL — 19 mi23. near Moline, IL — 19 mi34. Galva, IL — 20 mi45. near Rock Island, IL — 22 mi5
  1. near Le Claire, IA 16 mi (25 km)
  2. Kewanee, IL 19 mi (31 km)
  3. near Moline, IL 19 mi (31 km)
  4. Galva, IL 20 mi (32 km)
  5. near Rock Island, IL 22 mi (35 km)

Sources

* Hardiness zone 5b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.4511, -90.1486.