U.S. Frost Dates by Weather Station

NOAA station USC00116753 · Illinois

Frost Dates for Peru, IL

NOAA weather station Peru (USC00116753), Illinois · elevation 620 ft (189 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 1850% chance of a frost before it
  • Frost-free season176 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Peru, ILSpring: a frost after April 11 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 3 in 1 year out of 10, before October 18 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 176 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 24First frost ~Oct 18Frost season at Peru, ILSpring: a frost after April 11 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 3 in 1 year out of 10, before October 18 in half of the years, before October 28 in 9 years out of 10. Typical frost-free season: 176 days.JFMAMJJASONDLast frost ~Apr 24First frost ~Oct 18
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 3
50% (typical)April 24October 18
90% (likely)April 11October 28
Frost-free season (32°F, 50% chance)
176 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 23 (1 day earlier than the 30-year normal), typical first fall frost October 20 (2 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 Peru: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 8, 20% May 3, 30% April 30, 40% April 26, 50% April 24, 60% April 21, 70% April 19, 80% April 16, 90% April 11. Observed last spring frost in recent years: 2021 May 8, 2022 April 28, 2023 April 28, 2024 April 25, 2025 April 17, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 8Apr 24Apr 112021: May 82022: April 282023: April 282024: April 252025: April 172026: May 3Fall at Peru: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 9, 30% October 12, 40% October 15, 50% October 18, 60% October 20, 70% October 22, 80% October 25, 90% October 28. Observed first fall frost in recent years: 2021 October 23, 2022 October 8, 2023 October 30, 2024 October 16, 2025 October 24.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 18Oct 282021: October 232022: October 82023: 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 8October 23
2022April 28October 8
2023April 28October 30
2024April 25October 16
2025April 17October 24
2026May 3season not over yet

What these dates mean

May 8 is the cautious spring date, giving a gardener a small 10 % chance that a light frost will occur later and permitting the setting out of tender crops with modest risk. The median spring light-frost date is April 24, and the median fall light-frost date is October 18; each marks an even 50 % chance of a frost. For a careful schedule, the cautious fall date is October 3, when there is only a 10 % chance that a light frost has arrived earlier, allowing the final harvest of tender crops.

The 50 % hard-frost dates are April 13 in spring and October 28 in fall; these are the points at which a hard frost (28 °F) is as likely as not. Hard frost matters more than a light frost because temperatures at 28 °F can injure or kill plants that would survive a 32 °F light frost.

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 3" 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 Peru, ILNumbered nearest stations: 1 — Ottawa, IL — 10 mi; 2 — Princeton, IL — 18 mi; 3 — Paw Paw, IL — 23 mi; 4 — Walnut, IL — 29 mi; 5 — Minonk, IL — 30 mi.IA25 mi · 40 km1. Ottawa, IL — 10 mi12. Princeton, IL — 18 mi23. Paw Paw, IL — 23 mi34. Walnut, IL — 29 mi45. Minonk, IL — 30 mi5
  1. Ottawa, IL 10 mi (17 km)
  2. Princeton, IL 18 mi (29 km)
  3. Paw Paw, IL 23 mi (37 km)
  4. Walnut, IL 29 mi (47 km)
  5. Minonk, IL 30 mi (49 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: 41.3503, -89.1072.