U.S. Frost Dates by Weather Station

NOAA station USC00111475 · Illinois

Frost Dates for Chenoa, IL

NOAA weather station Chenoa (USC00111475), Illinois · elevation 719 ft (219 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 7only 1 spring in 10 still has a frost later
  • Typical last frostApril 2350% chance of a frost after it
  • Typical first fall frostOctober 1550% chance of a frost before it
  • Frost-free season174 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Chenoa, ILSpring: a frost after April 9 in 9 years out of 10, after April 23 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before September 29 in 1 year out of 10, before October 15 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 174 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 23First frost ~Oct 15Frost season at Chenoa, ILSpring: a frost after April 9 in 9 years out of 10, after April 23 in half of the years, after May 7 in 1 year out of 10. Fall: the first frost comes before September 29 in 1 year out of 10, before October 15 in half of the years, before October 29 in 9 years out of 10. Typical frost-free season: 174 days.JFMAMJJASONDLast frost ~Apr 23First frost ~Oct 15
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 27 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 7September 29
50% (typical)April 23October 15
90% (likely)April 9October 29
Frost-free season (32°F, 50% chance)
174 days
Hard frost (28°F), last in spring, 50% chance after
April 12
Hard frost (28°F), first in fall, 50% chance before
October 26

The last 15 years (2006–2020 normals)

Typical last frost April 23 (same as the 30-year normal), typical first fall frost October 18 (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 Chenoa: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 7, 20% May 2, 30% April 29, 40% April 25, 50% April 23, 60% April 21, 70% April 18, 80% April 14, 90% April 9. Observed last spring frost in recent years: 2021 April 22, 2023 April 26.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 7Apr 23Apr 92021: April 222023: April 26Fall at Chenoa: chance of a frost before this dateFall, chance of a frost before the date: 10% September 29, 20% October 5, 30% October 9, 40% October 12, 50% October 15, 60% October 18, 70% October 21, 80% October 23, 90% October 29. Observed first fall frost in recent years: 2021 November 3, 2022 October 19.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 29Oct 15Oct 292021: November 32022: October 19
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 22November 3
2022incomplete recordOctober 19
2023April 26incomplete record
2024no datano data
2025no datano data
2026no dataseason not over yet

What these dates mean

Setting out tender crops on April 9 in Chenoa is a gamble, because there is a 90 % chance of a light frost later than that date.

The 50 % dates are April 23 for spring and October 15 for fall; each marks an even-odds point for a light frost—later than April 23 in spring, earlier than October 15 in fall. For a cautious planting plan, the spring date of May 7 (10 % chance of a frost later) is used, and the fall date of September 29 (10 % chance of a frost earlier) signals when tender crops should be finished. The record spans 27 years, and the interval between the two 32 °F 50 % dates is 174 days.

A hard frost at 28 °F, noted by the median dates April 12 and October 26, can damage plants more severely than a light frost at 32 °F.

How to read the probabilities

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

  • Spring: "10% after May 7" 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 29" 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 Chenoa, ILNumbered nearest stations: 1 — Pontiac, IL — 10 mi; 2 — Normal, IL — 18 mi; 3 — Minonk, IL — 20 mi; 4 — Dwight, IL — 30 mi; 5 — Rantoul, IL — 42 mi.IN25 mi · 40 km1. Pontiac, IL — 10 mi12. Normal, IL — 18 mi23. Minonk, IL — 20 mi34. Dwight, IL — 30 mi45. Rantoul, IL — 42 mi5
  1. Pontiac, IL 10 mi (17 km)
  2. Normal, IL 18 mi (29 km)
  3. Minonk, IL 20 mi (33 km)
  4. Dwight, IL 30 mi (48 km)
  5. Rantoul, IL 42 mi (67 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: 40.7408, -88.7181.