U.S. Frost Dates by Weather Station

NOAA station USC00344019 · Oklahoma

Frost Dates for Helena, OK

NOAA weather station Helena 1 SSE (USC00344019), Oklahoma · elevation 1350 ft (412 m) · hardiness zone 7a*

  • Lower-risk planting dateafter April 23only 1 spring in 10 still has a frost later
  • Typical last frostApril 950% chance of a frost after it
  • Typical first fall frostOctober 3150% chance of a frost before it
  • Frost-free season205 daystypical year, 32°F
  • Hardiness zone7acalculated*

The year at a glance

Frost season at Helena, OKSpring: a frost after March 25 in 9 years out of 10, after April 9 in half of the years, after April 23 in 1 year out of 10. Fall: the first frost comes before October 18 in 1 year out of 10, before October 31 in half of the years, before November 13 in 9 years out of 10. Typical frost-free season: 205 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~Apr 9First frost ~Oct 31Frost season at Helena, OKSpring: a frost after March 25 in 9 years out of 10, after April 9 in half of the years, after April 23 in 1 year out of 10. Fall: the first frost comes before October 18 in 1 year out of 10, before October 31 in half of the years, before November 13 in 9 years out of 10. Typical frost-free season: 205 days.JFMAMJJASONDLast frost ~Apr 9First frost ~Oct 31
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)April 23October 18
50% (typical)April 9October 31
90% (likely)March 25November 13
Frost-free season (32°F, 50% chance)
205 days
Hard frost (28°F), last in spring, 50% chance after
March 31
Hard frost (28°F), first in fall, 50% chance before
November 8

The last 15 years (2006–2020 normals)

Typical last frost April 12 (3 days later than the 30-year normal), typical first fall frost October 30 (1 day earlier). Frost-free season 202 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 Helena: chance of a frost after this dateSpring, chance of a frost after the date: 10% April 23, 20% April 19, 30% April 15, 40% April 11, 50% April 9, 60% April 6, 70% April 3, 80% March 31, 90% March 25. Observed last spring frost in recent years: 2021 April 22, 2022 April 26, 2023 April 23, 2024 March 28, 2025 April 7, 2026 March 18.Spring: last frostChance of a frost after this date10%50%90%Apr 1May 1Apr 23Apr 9Mar 252021: April 222022: April 262023: April 232024: March 282025: April 72026: March 18Fall at Helena: chance of a frost before this dateFall, chance of a frost before the date: 10% October 18, 20% October 22, 30% October 26, 40% October 28, 50% October 31, 60% November 2, 70% November 5, 80% November 8, 90% November 13. Observed first fall frost in recent years: 2021 November 13, 2022 October 19, 2023 October 29, 2024 November 22, 2025 October 30.Fall: first frostChance of a frost before this date10%50%90%Nov 1Oct 18Oct 31Nov 132021: November 132022: October 192023: October 292024: November 222025: October 30
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 13
2022April 26October 19
2023April 23October 29
2024March 28November 22
2025April 7October 30
2026March 18season not over yet

What these dates mean

Setting out tender crops on the early spring date, March 25, is a gamble because there is a 90 % chance of a frost later than that date. Gardeners who wait until the cautious spring date, April 23, face only a 10 % chance of a frost later, making it the safer point to begin planting tender varieties.

The 50 % date in spring, April 9, marks the point at which a frost later than this date is as likely as not, while the 50 % date in fall, October 31, indicates an even chance of a frost earlier than this date. The cautious fall date, October 18, carries a 10 % chance that frost has already arrived, so finishing tender-crop harvests by then reduces risk. The hard-frost median dates, March 31 and November 8, are important because a 28 °F frost can damage plants that survive a light 32 °F frost.

How to read the probabilities

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

  • Spring: "10% after April 23" 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 18" 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 Helena, OKNumbered nearest stations: 1 — Enid, OK — 23 mi; 2 — Anthony, KS — 45 mi; 3 — Billings, OK — 45 mi; 4 — Watonga, OK — 48 mi; 5 — Mutual, OK — 55 mi.OKKS25 mi · 40 km1. Enid, OK — 23 mi12. Anthony, KS — 45 mi23. Billings, OK — 45 mi34. Watonga, OK — 48 mi45. Mutual, OK — 55 mi5
  1. Enid, OK 23 mi (37 km)
  2. Anthony, KS 45 mi (72 km)
  3. Billings, OK 45 mi (73 km)
  4. Watonga, OK 48 mi (77 km)
  5. Mutual, OK 55 mi (88 km)

Sources

* Hardiness zone 7a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 36.5381, -98.2661.