U.S. Frost Dates by Weather Station

NOAA station USW00014931 · Iowa

Frost Dates for Burlington (Airport), IA

NOAA weather station Burlington Municipal Airport (USW00014931), Iowa · elevation 692 ft (211 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 1only 1 spring in 10 still has a frost later
  • Typical last frostApril 1550% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season187 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Burlington (Airport), IASpring: a frost after April 2 in 9 years out of 10, after April 15 in half of the years, after May 1 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 20 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 187 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 15First frost ~Oct 20Frost season at Burlington (Airport), IASpring: a frost after April 2 in 9 years out of 10, after April 15 in half of the years, after May 1 in 1 year out of 10. Fall: the first frost comes before October 6 in 1 year out of 10, before October 20 in half of the years, before November 1 in 9 years out of 10. Typical frost-free season: 187 days.JFMAMJJASONDLast frost ~Apr 15First frost ~Oct 20
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 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 1October 6
50% (typical)April 15October 20
90% (likely)April 2November 1
Frost-free season (32°F, 50% chance)
187 days
Hard frost (28°F), last in spring, 50% chance after
April 5
Hard frost (28°F), first in fall, 50% chance before
October 31

The last 15 years (2006–2020 normals)

Typical last frost April 17 (2 days later than the 30-year normal), typical first fall frost October 22 (2 days later). Frost-free season 187 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 Burlington (Airport): chance of a frost after this dateSpring, chance of a frost after the date: 10% May 1, 20% April 27, 30% April 22, 40% April 19, 50% April 15, 60% April 13, 70% April 10, 80% April 6, 90% April 2. Observed last spring frost in recent years: 2021 April 22, 2022 April 26, 2023 April 24, 2024 April 5, 2025 April 8, 2026 April 20.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 1Apr 15Apr 22021: April 222022: April 262023: April 242024: April 52025: April 82026: April 20Fall at Burlington (Airport): chance of a frost before this dateFall, chance of a frost before the date: 10% October 6, 20% October 11, 30% October 15, 40% October 18, 50% October 20, 60% October 23, 70% October 25, 80% October 29, 90% November 1. Observed first fall frost in recent years: 2021 November 1, 2022 October 8, 2023 October 29, 2024 October 15.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 6Oct 20Nov 12021: November 12022: October 82023: October 292024: October 15
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 1
2022April 26October 8
2023April 24October 29
2024April 5October 15
2025April 8incomplete record
2026April 20season not over yet

What these dates mean

The 187 days between the 32°F 50% dates in Burlington (Airport) define the window in which light frosts are equally likely to have occurred or not. The spring 50% date is April 15, marking a 50% chance of a frost later than this date; the fall 50% date is October 20, marking a 50% chance of a frost earlier than this date. Gardeners can use these reference points to gauge the overall risk period for tender crops.

For a cautious approach, the spring light-frost date of May 1 carries only a 10% chance of a frost later, while the fall caution date of October 6 carries a 10% chance of a frost earlier. The hard-frost median dates are April 5 and October 31, and a hard frost at 28°F can damage plants more severely than a light frost at 32°F because the lower temperature is lethal to a broader range of tissue.

How to read the probabilities

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

  • Spring: "10% after May 1" 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 6" 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 Burlington (Airport), IANumbered nearest stations: 1 — near Burlington, IA — 1 mi; 2 — near Oquawka, IL — 9 mi; 3 — Fort Madison, IA — 16 mi; 4 — Mount Pleasant, IA — 26 mi; 5 — Monmouth, IL — 28 mi.ILMO25 mi · 40 km1. near Burlington, IA — 1 mi12. near Oquawka, IL — 9 mi23. Fort Madison, IA — 16 mi34. Mount Pleasant, IA — 26 mi45. Monmouth, IL — 28 mi5
  1. near Burlington, IA 1 mi (1 km)
  2. near Oquawka, IL 9 mi (14 km)
  3. Fort Madison, IA 16 mi (25 km)
  4. Mount Pleasant, IA 26 mi (41 km)
  5. Monmouth, IL 28 mi (45 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: 40.7833, -91.1253.