U.S. Frost Dates by Weather Station

NOAA station USC00146128 · Kansas

Frost Dates for Ottawa, KS

NOAA weather station Ottawa (USC00146128), Kansas · elevation 905 ft (276 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 1only 1 spring in 10 still has a frost later
  • Typical last frostApril 1850% chance of a frost after it
  • Typical first fall frostOctober 2050% chance of a frost before it
  • Frost-free season183 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Ottawa, KSSpring: a frost after April 5 in 9 years out of 10, after April 18 in half of the years, after May 1 in 1 year out of 10. Fall: the first frost comes before October 3 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: 183 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 18First frost ~Oct 20Frost season at Ottawa, KSSpring: a frost after April 5 in 9 years out of 10, after April 18 in half of the years, after May 1 in 1 year out of 10. Fall: the first frost comes before October 3 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: 183 days.JFMAMJJASONDLast frost ~Apr 18First 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 26 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 1October 3
50% (typical)April 18October 20
90% (likely)April 5November 1
Frost-free season (32°F, 50% chance)
183 days
Hard frost (28°F), last in spring, 50% chance after
April 8
Hard frost (28°F), first in fall, 50% chance before
October 30

The last 15 years (2006–2020 normals)

Typical last frost April 17 (1 day earlier than the 30-year normal), typical first fall frost October 22 (2 days later). Frost-free season 188 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 Ottawa: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 1, 20% April 27, 30% April 24, 40% April 21, 50% April 18, 60% April 16, 70% April 13, 80% April 10, 90% April 5. Observed last spring frost in recent years: 2021 April 23, 2022 April 26, 2023 April 24, 2025 April 9, 2026 March 29.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1May 1Apr 18Apr 52021: April 232022: April 262023: April 242025: April 92026: March 29Fall at Ottawa: chance of a frost before this dateFall, chance of a frost before the date: 10% October 3, 20% October 9, 30% October 14, 40% October 17, 50% October 20, 60% October 23, 70% October 26, 80% October 29, 90% November 1. Observed first fall frost in recent years: 2021 November 3, 2022 October 18, 2023 October 28, 2024 October 16, 2025 November 2.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Oct 3Oct 20Nov 12021: November 32022: October 182023: October 282024: October 162025: November 2
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 23November 3
2022April 26October 18
2023April 24October 28
2024incomplete recordOctober 16
2025April 9November 2
2026March 29season not over yet

What these dates mean

The 183 days between the 50% light-frost dates—April 18 and October 20—frame the period in Ottawa when tender crops can be planted, develop, and be harvested under typical conditions.

In this location the 50% dates are not frost dates; they simply mark the point where the chance of a light frost is even. For a cautious spring schedule gardeners should wait until the May 1 date, which carries only a 10 % chance of a later frost. In the fall the cautious endpoint is October 3, also a 10 % chance of an earlier frost, while the earlier April 5 and later November 1 dates each involve a 90 % chance and are gambles.

Hard frost at 28 °F, noted on April 8 and October 30, can damage plants that survive a 32 °F light frost.

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 3" 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 Ottawa, KSNumbered nearest stations: 1 — near Lawrence, KS — 23 mi; 2 — Garnett, KS — 23 mi; 3 — Topeka, KS — 37 mi; 4 — Iola, KS — 48 mi; 5 — near Kansas City, MO — 51 mi.KSMO25 mi · 40 km1. near Lawrence, KS — 23 mi12. Garnett, KS — 23 mi23. Topeka, KS — 37 mi34. Iola, KS — 48 mi45. near Kansas City, MO — 51 mi5
  1. near Lawrence, KS 23 mi (37 km)
  2. Garnett, KS 23 mi (37 km)
  3. Topeka, KS 37 mi (59 km)
  4. Iola, KS 48 mi (78 km)
  5. near Kansas City, MO 51 mi (82 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: 38.6133, -95.2808.