U.S. Frost Dates by Weather Station

NOAA station USC00130364 · Iowa

Frost Dates for Atlantic, IA

NOAA weather station Atlantic 1 NE (USC00130364), Iowa · elevation 1152 ft (351 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 15only 1 spring in 10 still has a frost later
  • Typical last frostApril 3050% chance of a frost after it
  • Typical first fall frostOctober 250% chance of a frost before it
  • Frost-free season153 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Atlantic, IASpring: a frost after April 17 in 9 years out of 10, after April 30 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before October 2 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 153 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 30First frost ~Oct 2Frost season at Atlantic, IASpring: a frost after April 17 in 9 years out of 10, after April 30 in half of the years, after May 15 in 1 year out of 10. Fall: the first frost comes before September 17 in 1 year out of 10, before October 2 in half of the years, before October 16 in 9 years out of 10. Typical frost-free season: 153 days.JFMAMJJASONDLast frost ~Apr 30First frost ~Oct 2
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 15September 17
50% (typical)April 30October 2
90% (likely)April 17October 16
Frost-free season (32°F, 50% chance)
153 days
Hard frost (28°F), last in spring, 50% chance after
April 22
Hard frost (28°F), first in fall, 50% chance before
October 12

The last 15 years (2006–2020 normals)

Typical last frost April 30 (same as the 30-year normal), typical first fall frost October 7 (5 days later). Frost-free season 158 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 Atlantic: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 15, 20% May 9, 30% May 6, 40% May 3, 50% April 30, 60% April 28, 70% April 25, 80% April 22, 90% April 17. Observed last spring frost in recent years: 2021 May 13, 2022 May 22, 2023 May 4, 2024 April 24, 2025 April 17, 2026 May 10.Spring: last frostChance of a frost after this date10%50%90%May 1May 15Apr 30Apr 172021: May 132022: May 222023: May 42024: April 242025: April 172026: May 10Fall at Atlantic: chance of a frost before this dateFall, chance of a frost before the date: 10% September 17, 20% September 23, 30% September 26, 40% September 29, 50% October 2, 60% October 4, 70% October 7, 80% October 11, 90% October 16. Observed first fall frost in recent years: 2021 September 25, 2022 September 28, 2023 October 10, 2024 October 7, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 17Oct 2Oct 162021: September 252022: September 282023: October 102024: October 72025: October 23
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 13September 25
2022May 22September 28
2023May 4October 10
2024April 24October 7
2025April 17October 23
2026May 10season not over yet

What these dates mean

The 153 days between the 50% dates in Atlantic – from April 30 to October 2 – mark the core period in which tender crops can be expected to grow without a light frost interrupting development. This span is derived from 30 years of NOAA records for the station.

For a cautious spring plan, the light-frost date of May 15 carries only a 10 % chance of a frost later, so tender seedlings are usually set out after that day; planting on April 17 would be a gamble with a 90 % chance of frost. In the fall, the cautious date to finish harvesting tender crops is September 17, when there is only a 10 % chance a frost has arrived; extending growth to October 16 would be a gamble with a 90 % chance of frost. A hard frost at 28 °F can damage plant tissues that survive a light frost at 32 °F, making the median hard-frost dates of April 22 and October 12 especially noteworthy.

How to read the probabilities

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

  • Spring: "10% after May 15" 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 17" 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 Atlantic, IANumbered nearest stations: 1 — Audubon, IA — 20 mi; 2 — Oakland, IA — 21 mi; 3 — Greenfield, IA — 30 mi; 4 — Red Oak, IA — 31 mi; 5 — Guthrie Center, IA — 31 mi.NEMO25 mi · 40 km1. Audubon, IA — 20 mi12. Oakland, IA — 21 mi23. Greenfield, IA — 30 mi34. Red Oak, IA — 31 mi45. Guthrie Center, IA — 31 mi5
  1. Audubon, IA 20 mi (33 km)
  2. Oakland, IA 21 mi (34 km)
  3. Greenfield, IA 30 mi (49 km)
  4. Red Oak, IA 31 mi (50 km)
  5. Guthrie Center, IA 31 mi (51 km)

Sources

* Hardiness zone 5a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 41.4175, -95.0042.