U.S. Frost Dates by Weather Station

NOAA station USC00250050 · Nebraska

Frost Dates for Ainsworth, NE

NOAA weather station Ainsworth (USC00250050), Nebraska · elevation 2510 ft (765 m) · hardiness zone 5b*

  • Lower-risk planting dateafter May 14only 1 spring in 10 still has a frost later
  • Typical last frostMay 250% chance of a frost after it
  • Typical first fall frostOctober 850% chance of a frost before it
  • Frost-free season158 daystypical year, 32°F
  • Hardiness zone5bcalculated*

The year at a glance

Frost season at Ainsworth, NESpring: a frost after April 19 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 8 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 158 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 2First frost ~Oct 8Frost season at Ainsworth, NESpring: a frost after April 19 in 9 years out of 10, after May 2 in half of the years, after May 14 in 1 year out of 10. Fall: the first frost comes before September 25 in 1 year out of 10, before October 8 in half of the years, before October 21 in 9 years out of 10. Typical frost-free season: 158 days.JFMAMJJASONDLast frost ~May 2First frost ~Oct 8
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 14September 25
50% (typical)May 2October 8
90% (likely)April 19October 21
Frost-free season (32°F, 50% chance)
158 days
Hard frost (28°F), last in spring, 50% chance after
April 22
Hard frost (28°F), first in fall, 50% chance before
October 18

The last 15 years (2006–2020 normals)

Typical last frost May 2 (same as the 30-year normal), typical first fall frost October 13 (5 days later). Frost-free season 161 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 Ainsworth: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 14, 20% May 10, 30% May 7, 40% May 4, 50% May 2, 60% April 30, 70% April 27, 80% April 23, 90% April 19. Observed last spring frost in recent years: 2022 May 21, 2023 May 2, 2024 April 21, 2025 April 19.Spring: last frostChance of a frost after this date10%50%90%May 1May 14May 2Apr 192022: May 212023: May 22024: April 212025: April 19Fall at Ainsworth: chance of a frost before this dateFall, chance of a frost before the date: 10% September 25, 20% September 30, 30% October 2, 40% October 5, 50% October 8, 60% October 11, 70% October 14, 80% October 17, 90% October 21. Observed first fall frost in recent years: 2022 October 16, 2023 October 6, 2024 October 13, 2025 October 28.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 25Oct 8Oct 212022: October 162023: October 62024: October 132025: October 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
2021incomplete recordincomplete record
2022May 21October 16
2023May 2October 6
2024April 21October 13
2025April 19October 28
2026incomplete recordseason not over yet

What these dates mean

The 158 days between the 50% dates in Ainsworth define the core frost-free interval for this station. The 50% light-frost dates are May 2 in spring and October 8 in fall; each marks the point where there is an even 50 % chance of a frost occurring later in spring or earlier in fall. These dates are not frost dates themselves but give gardeners a median reference for planning.

For a cautious spring schedule the 10 % chance date is May 14, when only a small chance of a later frost remains; planting on April 19 would be a gamble with a 90 % chance of a later frost. In fall the cautious date is September 25, when only a 10 % chance of an earlier frost exists; waiting until October 21 would be a gamble with a 90 % chance of an earlier frost. A hard frost at 28 °F, whose 50% dates are April 22 and October 18, matters more because temperatures that low can damage plant tissue that survives a 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 14" 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 25" 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 Ainsworth, NENumbered nearest stations: 1 — Springview, NE — 20 mi; 2 — Newport, NE — 27 mi; 3 — Elsmere, NE — 27 mi; 4 — near Valentine, NE — 42 mi; 5 — Atkinson, NE — 42 mi.SD25 mi · 40 km1. Springview, NE — 20 mi12. Newport, NE — 27 mi23. Elsmere, NE — 27 mi34. near Valentine, NE — 42 mi45. Atkinson, NE — 42 mi5
  1. Springview, NE 20 mi (33 km)
  2. Newport, NE 27 mi (43 km)
  3. Elsmere, NE 27 mi (44 km)
  4. near Valentine, NE 42 mi (67 km)
  5. Atkinson, NE 42 mi (68 km)

Sources

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

Station coordinates: 42.5522, -99.8556.