U.S. Frost Dates by Weather Station

NOAA station USC00293706 · New Mexico

Frost Dates for Grenville, NM

NOAA weather station Grenville (USC00293706), New Mexico · elevation 6002 ft (1829 m) · hardiness zone 6b*

  • Lower-risk planting dateafter May 20only 1 spring in 10 still has a frost later
  • Typical last frostMay 550% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season156 daystypical year, 32°F
  • Hardiness zone6bcalculated*

The year at a glance

Frost season at Grenville, NMSpring: a frost after April 23 in 9 years out of 10, after May 5 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 9 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 156 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 5First frost ~Oct 9Frost season at Grenville, NMSpring: a frost after April 23 in 9 years out of 10, after May 5 in half of the years, after May 20 in 1 year out of 10. Fall: the first frost comes before September 27 in 1 year out of 10, before October 9 in half of the years, before October 20 in 9 years out of 10. Typical frost-free season: 156 days.JFMAMJJASONDLast frost ~May 5First frost ~Oct 9
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 25 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 20September 27
50% (typical)May 5October 9
90% (likely)April 23October 20
Frost-free season (32°F, 50% chance)
156 days
Hard frost (28°F), last in spring, 50% chance after
April 26
Hard frost (28°F), first in fall, 50% chance before
October 17

The last 15 years (2006–2020 normals)

Typical last frost May 4 (1 day earlier than the 30-year normal), typical first fall frost October 11 (2 days later). Frost-free season 157 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 Grenville: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 20, 20% May 14, 30% May 11, 40% May 8, 50% May 5, 60% May 2, 70% April 30, 80% April 27, 90% April 23. Observed last spring frost in recent years: 2022 May 21.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 20May 5Apr 232022: May 21Fall at Grenville: 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 6, 50% October 9, 60% October 11, 70% October 13, 80% October 16, 90% October 20.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 9Oct 20
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
2021no datano data
2022May 21no data
2023no datano data
2024no datano data
2025no datano data
2026no dataseason not over yet

What these dates mean

Setting out tender crops on the early spring date of April 23 in Grenville is a gamble; there is a 90 % chance that a light frost will occur later, so seedlings are likely to be damaged. The later spring date of May 20 carries only a 10 % chance of a frost after that day, making it the cautious date for planting tender varieties.

The 50% light-frost date in spring is May 5, meaning a light frost is equally likely to arrive before or after that day. In fall the 50% light-frost date is October 9. The cautious fall date for finishing tender crops is September 27, when there is only a 10 % chance that a frost has already arrived; waiting until October 20 would be a gamble with a 90 % chance of frost earlier.

Hard frosts, measured at 28 °F, are more damaging than light frosts at 32 °F; the median hard-frost dates are April 26 in spring and October 17 in fall, indicating when the risk of a damaging freeze becomes even.

How to read the probabilities

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

  • Spring: "10% after May 20" 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 Grenville, NMNumbered nearest stations: 1 — Kim 10 SSE, CO — 40 mi; 2 — Raton, NM — 50 mi; 3 — Amistad, NM — 55 mi; 4 — Mosquero, NM — 58 mi; 5 — near Trinidad, CO — 61 mi.NMCOTXOK25 mi · 40 km1. Kim 10 SSE, CO — 40 mi12. Raton, NM — 50 mi23. Amistad, NM — 55 mi34. Mosquero, NM — 58 mi45. near Trinidad, CO — 61 mi5
  1. Kim 10 SSE, CO 40 mi (65 km)
  2. Raton, NM 50 mi (81 km)
  3. Amistad, NM 55 mi (89 km)
  4. Mosquero, NM 58 mi (93 km)
  5. near Trinidad, CO 61 mi (98 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: 36.5939, -103.6192.