U.S. Frost Dates by Weather Station

NOAA station USC00132573 · Iowa

Frost Dates for Eldora, IA

NOAA weather station Eldora (USC00132573), Iowa · elevation 1073 ft (327 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 8only 1 spring in 10 still has a frost later
  • Typical last frostApril 2750% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season165 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Eldora, IASpring: a frost after April 13 in 9 years out of 10, after April 27 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 10 in half of the years, before October 22 in 9 years out of 10. Typical frost-free season: 165 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 27First frost ~Oct 10Frost season at Eldora, IASpring: a frost after April 13 in 9 years out of 10, after April 27 in half of the years, after May 8 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 10 in half of the years, before October 22 in 9 years out of 10. Typical frost-free season: 165 days.JFMAMJJASONDLast frost ~Apr 27First frost ~Oct 10
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 8September 27
50% (typical)April 27October 10
90% (likely)April 13October 22
Frost-free season (32°F, 50% chance)
165 days
Hard frost (28°F), last in spring, 50% chance after
April 16
Hard frost (28°F), first in fall, 50% chance before
October 21

The last 15 years (2006–2020 normals)

Typical last frost April 28 (1 day later than the 30-year normal), typical first fall frost October 14 (4 days later). Frost-free season 168 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 Eldora: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 8, 20% May 4, 30% May 2, 40% April 30, 50% April 27, 60% April 23, 70% April 20, 80% April 17, 90% April 13. Observed last spring frost in recent years: 2021 April 25, 2022 April 27.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 8Apr 27Apr 132021: April 252022: April 27Fall at Eldora: chance of a frost before this dateFall, chance of a frost before the date: 10% September 27, 20% October 1, 30% October 4, 40% October 7, 50% October 10, 60% October 12, 70% October 15, 80% October 19, 90% October 22. Observed first fall frost in recent years: 2021 October 17, 2022 September 28.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 10Oct 222021: October 172022: September 28
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 25October 17
2022April 27September 28
2023incomplete recordno data
2024no datano data
2025no datano data
2026no dataseason not over yet

What these dates mean

The 165 days between the 50% dates in Eldora frame the window when a light frost (32 °F) is less likely than not, running from the spring median of April 27 to the fall median of October 10. Within that span gardeners can expect a lower overall probability of light frost, while outside of it the odds increase in either direction.

The cautious spring date for setting out tender crops is May 8, when there is only a 10 % chance of a later light frost; planting on April 13 carries a 90 % chance and is a gamble. In the fall, the cautious date to finish harvesting tender crops is September 27, with a 10 % chance of an earlier light frost, whereas October 22 involves a 90 % gamble.

A hard frost at 28 °F is more damaging than a light frost because it can injure plants that survive 32 °F. The 50% hard-frost dates are April 16 in spring and October 21 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 May 8" 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 27" 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 Eldora, IANumbered nearest stations: 1 — Iowa Falls, IA — 13 mi; 2 — Grundy Center, IA — 17 mi; 3 — Marshalltown, IA — 23 mi; 4 — Hampton, IA — 28 mi; 5 — Allison, IA — 31 mi.25 mi · 40 km1. Iowa Falls, IA — 13 mi12. Grundy Center, IA — 17 mi23. Marshalltown, IA — 23 mi34. Hampton, IA — 28 mi45. Allison, IA — 31 mi5
  1. Iowa Falls, IA 13 mi (21 km)
  2. Grundy Center, IA 17 mi (28 km)
  3. Marshalltown, IA 23 mi (36 km)
  4. Hampton, IA 28 mi (44 km)
  5. Allison, IA 31 mi (49 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: 42.3653, -93.0972.