U.S. Frost Dates by Weather Station

NOAA station USC00112687 · Illinois

Frost Dates for Effingham, IL

NOAA weather station Effingham 3 SW (USC00112687), Illinois · elevation 625 ft (191 m) · hardiness zone 6b*

  • Lower-risk planting dateafter April 29only 1 spring in 10 still has a frost later
  • Typical last frostApril 1350% 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 zone6bcalculated*

The year at a glance

Frost season at Effingham, ILSpring: a frost after April 1 in 9 years out of 10, after April 13 in half of the years, after April 29 in 1 year out of 10. Fall: the first frost comes before October 9 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 13First frost ~Oct 24Frost season at Effingham, ILSpring: a frost after April 1 in 9 years out of 10, after April 13 in half of the years, after April 29 in 1 year out of 10. Fall: the first frost comes before October 9 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 13First 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.

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)April 29October 9
50% (typical)April 13October 24
90% (likely)April 1November 5
Frost-free season (32°F, 50% chance)
191 days
Hard frost (28°F), last in spring, 50% chance after
April 2
Hard frost (28°F), first in fall, 50% chance before
November 1

The last 15 years (2006–2020 normals)

Typical last frost April 11 (2 days earlier than the 30-year normal), typical first fall frost October 26 (2 days later). Frost-free season 195 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 Effingham: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 29, 20% April 23, 30% April 19, 40% April 16, 50% April 13, 60% April 11, 70% April 7, 80% April 5, 90% April 1.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 29Apr 13Apr 1Fall at Effingham: chance of a frost before this dateFall, chance of a frost before the date: 10% October 9, 20% October 15, 30% October 18, 40% October 22, 50% October 24, 60% October 26, 70% October 28, 80% October 31, 90% November 5.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 9Oct 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

Planting tender crops on April 1 in Effingham is a gamble, because there is a 90% chance of a light frost later than that date. By contrast, the cautious date for setting out tender crops is April 29, when only a 10% chance of a light frost remains.

The 50% date for spring light frost is April 13, representing the point at which the probability of a light frost reaches 50%. In the fall, the cautious date to finish harvesting tender crops is October 9, with a 10% chance that a light frost has already arrived, while the 50% fall date is October 24, where the chance of a light frost earlier than that date is 50%.

Hard frost, recorded at 28 °F, matters more than light frost because it can damage or kill plants that survive a 32 °F frost; the 50% hard-frost dates are April 2 in spring and November 1 in fall.

How to read the probabilities

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

  • Spring: "10% after April 29" 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 9" 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 Effingham, ILNumbered nearest stations: 1 — Windsor, IL — 23 mi; 2 — Ramsey, IL — 26 mi; 3 — Charleston, IL — 35 mi; 4 — Salem, IL — 37 mi; 5 — Olney, IL — 41 mi.IN25 mi · 40 km1. Windsor, IL — 23 mi12. Ramsey, IL — 26 mi23. Charleston, IL — 35 mi34. Salem, IL — 37 mi45. Olney, IL — 41 mi5
  1. Windsor, IL 23 mi (37 km)
  2. Ramsey, IL 26 mi (41 km)
  3. Charleston, IL 35 mi (56 km)
  4. Salem, IL 37 mi (60 km)
  5. Olney, IL 41 mi (66 km)

Sources

* Hardiness zone 6b: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 39.1181, -88.6244.