U.S. Frost Dates by Weather Station

NOAA station USC00051121 · Colorado

Frost Dates for Burlington, CO

NOAA weather station Burlington (USC00051121), Colorado · elevation 4162 ft (1269 m) · hardiness zone 6a*

  • Lower-risk planting dateafter May 19only 1 spring in 10 still has a frost later
  • Typical last frostMay 650% chance of a frost after it
  • Typical first fall frostOctober 950% chance of a frost before it
  • Frost-free season155 daystypical year, 32°F
  • Hardiness zone6acalculated*

The year at a glance

Frost season at Burlington, COSpring: a frost after April 23 in 9 years out of 10, after May 6 in half of the years, after May 19 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: 155 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 6First frost ~Oct 9Frost season at Burlington, COSpring: a frost after April 23 in 9 years out of 10, after May 6 in half of the years, after May 19 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: 155 days.JFMAMJJASONDLast frost ~May 6First 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.Today

Frost dates (32°F)

Probability of frost, based on 29 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 19September 27
50% (typical)May 6October 9
90% (likely)April 23October 20
Frost-free season (32°F, 50% chance)
155 days
Hard frost (28°F), last in spring, 50% chance after
April 27
Hard frost (28°F), first in fall, 50% chance before
October 18

The last 15 years (2006–2020 normals)

Typical last frost May 6 (same as the 30-year normal), typical first fall frost October 13 (4 days later). Frost-free season 159 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 Burlington: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 19, 20% May 14, 30% May 11, 40% May 9, 50% May 6, 60% May 3, 70% May 1, 80% April 28, 90% April 23. Observed last spring frost in recent years: 2021 April 25, 2022 May 22, 2023 April 24, 2024 May 4, 2025 April 20, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 19May 6Apr 232021: April 252022: May 222023: April 242024: May 42025: April 202026: May 7Fall at Burlington: 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 12, 70% October 14, 80% October 17, 90% October 20. Observed first fall frost in recent years: 2021 October 14, 2022 October 17, 2023 October 14, 2024 October 31, 2025 October 19.Fall: first frostChance of a frost before this date10%50%90%Oct 1Nov 1Sep 27Oct 9Oct 202021: October 142022: October 172023: October 142024: October 312025: October 19
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 25October 14
2022May 22October 17
2023April 24October 14
2024May 4October 31
2025April 20October 19
2026May 7season not over yet

What these dates mean

May 19 is the cautious spring date, with only a 10 percent chance that a light frost (32 °F) will occur later, allowing tender crops to be set out while risk remains low.

The 50 percent spring date is May 6; there is a 50 percent chance of a light frost later than this date. In the fall, September 27 is the cautious date, offering a 10 percent chance that a light frost has arrived earlier, so harvesting tender crops can be finished with confidence. The 50 percent fall date is October 9; there is a 50 percent chance of a light frost earlier than this date. Hard-frost median dates are April 27 in spring and October 18 in fall, and they mark when a 28 °F frost becomes as likely as not.

Because a 28 °F frost can damage plant tissue that survives a 32 °F light frost, hard frost presents a greater threat to tender crops than 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 19" 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 Burlington, CONumbered nearest stations: 1 — Bonny Dam 2 NE, CO — 25 mi; 2 — Goodland, KS — 30 mi; 3 — Joes, CO — 33 mi; 4 — Sharon Springs, KS — 39 mi; 5 — Saint Francis, KS — 40 mi.COKSNE25 mi · 40 km1. Bonny Dam 2 NE, CO — 25 mi12. Goodland, KS — 30 mi23. Joes, CO — 33 mi34. Sharon Springs, KS — 39 mi45. Saint Francis, KS — 40 mi5
  1. Bonny Dam 2 NE, CO 25 mi (41 km)
  2. Goodland, KS 30 mi (49 km)
  3. Joes, CO 33 mi (53 km)
  4. Sharon Springs, KS 39 mi (63 km)
  5. Saint Francis, KS 40 mi (64 km)

Sources

* Hardiness zone 6a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 39.3061, -102.2608.