U.S. Frost Dates by Weather Station

NOAA station USC00113262 · Illinois

Frost Dates for Freeport, IL

NOAA weather station Freeport Waste WTP (USC00113262), Illinois · elevation 750 ft (229 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 11only 1 spring in 10 still has a frost later
  • Typical last frostApril 2650% chance of a frost after it
  • Typical first fall frostOctober 1350% chance of a frost before it
  • Frost-free season169 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Freeport, ILSpring: a frost after April 11 in 9 years out of 10, after April 26 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 13 in half of the years, before October 26 in 9 years out of 10. Typical frost-free season: 169 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 26First frost ~Oct 13Frost season at Freeport, ILSpring: a frost after April 11 in 9 years out of 10, after April 26 in half of the years, after May 11 in 1 year out of 10. Fall: the first frost comes before September 30 in 1 year out of 10, before October 13 in half of the years, before October 26 in 9 years out of 10. Typical frost-free season: 169 days.JFMAMJJASONDLast frost ~Apr 26First frost ~Oct 13
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 11September 30
50% (typical)April 26October 13
90% (likely)April 11October 26
Frost-free season (32°F, 50% chance)
169 days
Hard frost (28°F), last in spring, 50% chance after
April 14
Hard frost (28°F), first in fall, 50% chance before
October 24

The last 15 years (2006–2020 normals)

Typical last frost April 28 (2 days later than the 30-year normal), typical first fall frost October 15 (2 days later). Frost-free season 171 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 Freeport: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 11, 20% May 6, 30% May 2, 40% April 30, 50% April 26, 60% April 23, 70% April 19, 80% April 16, 90% April 11. Observed last spring frost in recent years: 2021 May 8, 2022 April 28, 2023 April 27, 2024 April 25, 2025 April 16, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 11Apr 26Apr 112021: May 82022: April 282023: April 272024: April 252025: April 162026: May 7Fall at Freeport: chance of a frost before this dateFall, chance of a frost before the date: 10% September 30, 20% October 4, 30% October 8, 40% October 11, 50% October 13, 60% October 16, 70% October 18, 80% October 21, 90% October 26. Observed first fall frost in recent years: 2021 October 23, 2022 October 8, 2023 October 10, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 30Oct 13Oct 262021: October 232022: October 82023: October 102024: 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 8October 23
2022April 28October 8
2023April 27October 10
2024April 25October 16
2025April 16October 24
2026May 7season not over yet

What these dates mean

The cautious fall date in Freeport for finishing the harvest is September 30, when there is only a 10 % chance a light frost has arrived.

The 50 % light-frost dates—April 26 in spring and October 13 in fall—are the points at which a gardener faces an even likelihood of frost later (spring) or earlier (fall). For a low-risk schedule, the cautious spring date for setting out tender crops is May 11, and the cautious fall date for ending tender crops is September 30. The median hard-frost dates are April 14 and October 24. The record covers 30 years, and the interval between the two 32 °F 50 % dates is 169 days, representing the typical frost-free window.

A hard frost at 28 °F can damage plants that survive a 32 °F light frost, so the hard-frost dates are a higher-risk threshold.

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 September 30" 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 Freeport, ILNumbered nearest stations: 1 — Stockton, IL — 21 mi; 2 — Brodhead, WI — 25 mi; 3 — Rockford, IL — 27 mi; 4 — Beloit, WI — 33 mi; 5 — near Janesville, WI — 36 mi.ILWIIA25 mi · 40 km1. Stockton, IL — 21 mi12. Brodhead, WI — 25 mi23. Rockford, IL — 27 mi34. Beloit, WI — 33 mi45. near Janesville, WI — 36 mi5
  1. Stockton, IL 21 mi (34 km)
  2. Brodhead, WI 25 mi (40 km)
  3. Rockford, IL 27 mi (44 km)
  4. Beloit, WI 33 mi (52 km)
  5. near Janesville, WI 36 mi (58 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: 42.2972, -89.6039.