U.S. Frost Dates by Weather Station

NOAA station USC00131257 · Iowa

Frost Dates for Cascade, IA

NOAA weather station Cascade (USC00131257), Iowa · elevation 814 ft (248 m) · hardiness zone 5a*

  • Lower-risk planting dateafter May 12only 1 spring in 10 still has a frost later
  • Typical last frostApril 2850% chance of a frost after it
  • Typical first fall frostOctober 1050% chance of a frost before it
  • Frost-free season164 daystypical year, 32°F
  • Hardiness zone5acalculated*

The year at a glance

Frost season at Cascade, IASpring: a frost after April 12 in 9 years out of 10, after April 28 in half of the years, after May 12 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 10 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 164 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 28First frost ~Oct 10Frost season at Cascade, IASpring: a frost after April 12 in 9 years out of 10, after April 28 in half of the years, after May 12 in 1 year out of 10. Fall: the first frost comes before September 28 in 1 year out of 10, before October 10 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 164 days.JFMAMJJASONDLast frost ~Apr 28First 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 28 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 12September 28
50% (typical)April 28October 10
90% (likely)April 12October 21
Frost-free season (32°F, 50% chance)
164 days
Hard frost (28°F), last in spring, 50% chance after
April 15
Hard frost (28°F), first in fall, 50% chance before
October 20

The last 15 years (2006–2020 normals)

Typical last frost April 27 (1 day earlier than the 30-year normal), typical first fall frost October 12 (2 days later). Frost-free season 169 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 Cascade: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 12, 20% May 6, 30% May 3, 40% April 30, 50% April 28, 60% April 24, 70% April 21, 80% April 17, 90% April 12. Observed last spring frost in recent years: 2021 May 12, 2022 April 27, 2023 April 27, 2024 April 23, 2025 April 18, 2026 May 3.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 12Apr 28Apr 122021: May 122022: April 272023: April 272024: April 232025: April 182026: May 3Fall at Cascade: chance of a frost before this dateFall, chance of a frost before the date: 10% September 28, 20% October 1, 30% October 4, 40% October 7, 50% October 10, 60% October 11, 70% October 14, 80% October 16, 90% October 21. Observed first fall frost in recent years: 2021 October 23, 2022 September 29, 2025 October 23.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 28Oct 10Oct 212021: October 232022: September 292025: 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 12October 23
2022April 27September 29
2023April 27incomplete record
2024April 23incomplete record
2025April 18October 23
2026May 3season not over yet

What these dates mean

September 28 marks the cautious fall date for finishing the harvest of tender crops in Cascade, Iowa, because there is only a 10% chance that a light frost has already arrived by then.

For light frost the 50% dates—April 28 in spring and October 10 in fall—indicate the point at which the chance of a frost is even; they are not frost dates but help gauge risk. A gardener who follows a cautious plan would wait until May 12, when the chance of a frost later than that date is 10%, before setting out tender crops in spring, and would aim to complete tender-crop harvest by September 28 in the fall. The hard-frost median dates, April 15 and October 20, signal when temperatures can drop to 28 °F, a level that can damage plants more severely than the 32 °F light frost because it freezes 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 12" 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 28" 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 Cascade, IANumbered nearest stations: 1 — Dubuque, IA — 17 mi; 2 — Maquoketa, IA — 23 mi; 3 — Dubuque Lock and Dam 11, IA — 25 mi; 4 — near Manchester, IA — 26 mi; 5 — near Bellevue, IA — 30 mi.IAWIIL25 mi · 40 km1. Dubuque, IA — 17 mi12. Maquoketa, IA — 23 mi23. Dubuque Lock and Dam 11, IA — 25 mi34. near Manchester, IA — 26 mi45. near Bellevue, IA — 30 mi5
  1. Dubuque, IA 17 mi (28 km)
  2. Maquoketa, IA 23 mi (38 km)
  3. Dubuque Lock and Dam 11, IA 25 mi (40 km)
  4. near Manchester, IA 26 mi (41 km)
  5. near Bellevue, IA 30 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: 42.2978, -91.0117.