U.S. Frost Dates by Weather Station

NOAA station USW00094822 · Illinois

Frost Dates for Rockford, IL

NOAA weather station Rockford Greater Rockford Airport (USW00094822), Illinois · elevation 730 ft (223 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 8only 1 spring in 10 still has a frost later
  • Typical last frostApril 2450% chance of a frost after it
  • Typical first fall frostOctober 1750% chance of a frost before it
  • Frost-free season174 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Rockford, ILSpring: a frost after April 10 in 9 years out of 10, after April 24 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before October 2 in 1 year out of 10, before October 17 in half of the years, before October 30 in 9 years out of 10. Typical frost-free season: 174 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 24First frost ~Oct 17Frost season at Rockford, ILSpring: a frost after April 10 in 9 years out of 10, after April 24 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before October 2 in 1 year out of 10, before October 17 in half of the years, before October 30 in 9 years out of 10. Typical frost-free season: 174 days.JFMAMJJASONDLast frost ~Apr 24First frost ~Oct 17
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 8October 2
50% (typical)April 24October 17
90% (likely)April 10October 30
Frost-free season (32°F, 50% chance)
174 days
Hard frost (28°F), last in spring, 50% chance after
April 13
Hard frost (28°F), first in fall, 50% chance before
October 28

The last 15 years (2006–2020 normals)

Typical last frost April 24 (same as the 30-year normal), typical first fall frost October 20 (3 days later). Frost-free season 179 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 Rockford: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 8, 20% May 2, 30% April 30, 40% April 27, 50% April 24, 60% April 21, 70% April 18, 80% April 15, 90% April 10. Observed last spring frost in recent years: 2021 April 22, 2022 April 27, 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 8Apr 24Apr 102021: April 222022: April 272023: April 272024: April 252025: April 162026: May 7Fall at Rockford: chance of a frost before this dateFall, chance of a frost before the date: 10% October 2, 20% October 8, 30% October 12, 40% October 14, 50% October 17, 60% October 19, 70% October 22, 80% October 26, 90% October 30. Observed first fall frost in recent years: 2021 October 23, 2022 October 8, 2023 October 10, 2024 October 16, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 2Oct 17Oct 302021: October 232022: October 82023: October 102024: October 162025: October 23
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 8
2023April 27October 10
2024April 25October 16
2025April 16October 23
2026May 7season not over yet

What these dates mean

Setting out tender crops on April 10 in Rockford is a gamble, because there is a 90% chance of a frost later than that date. The 50% spring light-frost date is April 24, meaning a gardener faces an even chance of a frost after this point, while the 50% fall light-frost date is October 17, with an even chance of a frost before it. The cautious spring date for tender crops is May 8, when only a 10% chance of a later frost remains, and the cautious fall date for finishing tender harvests is October 2, with only a 10% chance that a frost has arrived earlier. Hard frost, defined at 28 °F, can injure plants that tolerate a light frost at 32 °F, so the median hard-frost dates of April 13 and October 28 are especially important for growers.

How to read the probabilities

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

  • Spring: "10% after May 8" 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 Rockford, ILNumbered nearest stations: 1 — Rochelle, IL — 19 mi; 2 — Beloit, WI — 22 mi; 3 — De Kalb, IL — 24 mi; 4 — Freeport, IL — 27 mi; 5 — near Janesville, WI — 31 mi.WIIA25 mi · 40 km1. Rochelle, IL — 19 mi12. Beloit, WI — 22 mi23. De Kalb, IL — 24 mi34. Freeport, IL — 27 mi45. near Janesville, WI — 31 mi5
  1. Rochelle, IL 19 mi (31 km)
  2. Beloit, WI 22 mi (35 km)
  3. De Kalb, IL 24 mi (39 km)
  4. Freeport, IL 27 mi (44 km)
  5. near Janesville, WI 31 mi (50 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: 42.1928, -89.0931.