When Is Your First Fall Frost?
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GardenSays
Your average first fall frost in Minneapolis, MN is around Oct 5 — plan fall crops and frost protection back from that date.
- First frost (typ.)
- Oct 5
- Watch nights from
- Sep 21
- Season length
- 153 days
In Minneapolis, MN the first killing frost of fall typically arrives around Oct 5. Everything frost-sensitive — tomatoes, peppers, basil, cucumbers — needs to be harvested or protected by then; cool-season crops and fall plantings are timed by counting back from it.
- These dates are NOAA climate normals (long-term averages), not a forecast. For frost risk tonight, check your local forecast — the NWS issues frost advisories when surface temperatures are expected in the mid-30s °F, because frost can form on plants before the air officially hits 32°F.
Calculated result · 4 verified sources · No live weather · Checked 2026-07-17 · How we decide
Why
From about two weeks before (Sep 21), start watching nightly forecasts: one cold night can end the warm-season garden while the following weeks stay mild.
- An "average" frost date is roughly a coin flip: in about half of years, frost still comes after the average last-frost date. Buffers turn that coin flip into good odds.
- Three different events: frost (ice on leaves, possible with air temps in the mid-30s °F) burns tender crops; a freeze at 32°F kills tender and very-tender crops; a hard freeze at 28°F or below kills most unprotected vegetation (NWS). Hardy crops like peas and spinach shrug off frost but not a prolonged hard freeze.
- Fall frosts are often isolated: protecting plants through the first cold night can buy several more mild weeks of harvest.
When this doesn't apply
- Microclimates shift these dates: low spots and frost pockets run 1-2 weeks riskier, urban cores and near-water gardens 1-2 weeks safer.
How this was calculated
- 1. Average last spring frostMay 5Source guidance
Minneapolis, MN: typical last 32°F morning, NOAA 1991-2020 normals
- 2. Average first fall frostOct 5Source guidance
Minneapolis, MN: typical first 32°F morning of fall
- 3. Growing season153 daysCalculated result
Days between the average last and first frost
Data sources
- NOAA NCEI — 1991-2020 U.S. Climate Normals (freeze date probabilities) (checked 2026-07-15)
- National Gardening Association — frost date lookup (checked 2026-07-15)
- NOAA National Weather Service — Frost Advisory (glossary) — Frost advisories are issued when widespread frost is expected; surface temperatures are usually in the mid 30s Fahrenheit. (checked 2026-07-16)
- NOAA National Weather Service — Hard Freeze (glossary) — A hard freeze occurs when the surface air temperature reaches 28°F or lower for an extended period, killing most types of vegetation. (checked 2026-07-17)
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