U.S. Frost Dates by Weather Station

NOAA station USC00116910 · Illinois

Frost Dates for Pontiac, IL

NOAA weather station Pontiac (USC00116910), Illinois · elevation 650 ft (198 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 2only 1 spring in 10 still has a frost later
  • Typical last frostApril 1650% chance of a frost after it
  • Typical first fall frostOctober 2450% chance of a frost before it
  • Frost-free season191 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Pontiac, ILSpring: a frost after April 3 in 9 years out of 10, after April 16 in half of the years, after May 2 in 1 year out of 10. Fall: the first frost comes before October 12 in 1 year out of 10, before October 24 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 191 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 16First frost ~Oct 24Frost season at Pontiac, ILSpring: a frost after April 3 in 9 years out of 10, after April 16 in half of the years, after May 2 in 1 year out of 10. Fall: the first frost comes before October 12 in 1 year out of 10, before October 24 in half of the years, before November 5 in 9 years out of 10. Typical frost-free season: 191 days.JFMAMJJASONDLast frost ~Apr 16First frost ~Oct 24
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.Today

Frost dates (32°F)

Probability of frost, based on 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 2October 12
50% (typical)April 16October 24
90% (likely)April 3November 5
Frost-free season (32°F, 50% chance)
191 days
Hard frost (28°F), last in spring, 50% chance after
April 4
Hard frost (28°F), first in fall, 50% chance before
November 3

The last 15 years (2006–2020 normals)

Typical last frost April 16 (same as the 30-year normal), typical first fall frost October 27 (3 days later). Frost-free season 192 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 Pontiac: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 2, 20% April 26, 30% April 22, 40% April 19, 50% April 16, 60% April 13, 70% April 10, 80% April 7, 90% April 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 2Apr 16Apr 3Fall at Pontiac: chance of a frost before this dateFall, chance of a frost before the date: 10% October 12, 20% October 17, 30% October 20, 40% October 22, 50% October 24, 60% October 27, 70% October 30, 80% November 1, 90% November 5.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 12Oct 24Nov 5
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.

What these dates mean

October 12 marks the cautious fall date in Pontiac for finishing the harvest, when there is only a 10 % chance that a light frost has already arrived.

For tender crops the cautious spring date is May 2, a 10 % chance of a light frost later, while the gamble date of April 3 carries a 90 % chance. The median light-frost dates are April 16 and October 24; they represent even odds of frost occurring. The 50 % hard-frost dates are April 4 and November 3, indicating the point at which a 28 °F frost is equally likely to have happened or not.

A hard frost at 28 °F can damage plants that survive a light frost at 32 °F, making it a more critical threshold 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 2" 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 12" 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 Pontiac, ILNumbered nearest stations: 1 — Chenoa, IL — 10 mi; 2 — Dwight, IL — 20 mi; 3 — Minonk, IL — 21 mi; 4 — Normal, IL — 28 mi; 5 — Ottawa, IL — 34 mi.IN25 mi · 40 km1. Chenoa, IL — 10 mi12. Dwight, IL — 20 mi23. Minonk, IL — 21 mi34. Normal, IL — 28 mi45. Ottawa, IL — 34 mi5
  1. Chenoa, IL 10 mi (17 km)
  2. Dwight, IL 20 mi (32 km)
  3. Minonk, IL 21 mi (34 km)
  4. Normal, IL 28 mi (45 km)
  5. Ottawa, IL 34 mi (55 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: 40.8778, -88.6364.