Question 1

What does "last frost date" mean?

Accepted Answer

The last frost date is the average date in spring after which your area is unlikely to see temperatures at or below 32°F. It marks the start of the safe planting window for frost-sensitive crops. This is a statistical average from 30 years of NOAA data — not a guarantee for any single year.

Question 2

Is this frost date guaranteed?

Accepted Answer

No. The date shown is a 50% probability estimate based on 30-year NOAA Climate Normals. That means, on average, half the years will have a frost after this date in spring (or before this date in fall). Always watch the 10-day forecast before planting tender crops.

Question 3

What should I plant before my last spring frost?

Accepted Answer

Cool-season crops that tolerate light frost can be planted 2–6 weeks before your last frost date: peas, spinach, kale, broccoli, cabbage, carrots, and lettuce. Hardy bulbs like garlic and onion sets can also go in before last frost.

Question 4

What should I plant after my last spring frost?

Accepted Answer

Wait until after your last frost date for warm-season crops: tomatoes, peppers, cucumbers, squash, beans, corn, basil, and eggplant. These crops are killed or stunted by even light frost.

Question 5

How accurate are frost date averages?

Accepted Answer

NOAA Climate Normals are based on 30 years of daily observations (1991–2020). They're the best publicly available estimate for planning purposes, but local microclimates (low spots, proximity to water, urban heat) can shift your effective frost date by 1–2 weeks.

Question 6

What's the difference between light frost and hard frost?

Accepted Answer

A light frost occurs when temperatures dip just below 32°F for a short period. Many cool-season crops survive. A hard frost (below 28°F for several hours) kills most vegetables and many perennials. The dates shown here are for the 32°F threshold.

Question 7

How do I protect plants from a late frost?

Accepted Answer

Cover tender plants with frost cloth, old bed sheets, or row covers before sunset. Remove covers in the morning once temperatures rise above 32°F. A cold frame or wall-of-water teepee can extend the season by 4–6 weeks.

Question 8

Why does my zip code show a different frost date than my neighbor?

Accepted Answer

Frost dates are matched to the nearest NOAA weather station. If your zip code and your neighbor's zip code map to different stations, you may see different dates. Stations can be 5–50km from the location they represent.

Frost data not available for Sunburst, MT

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Frost data not available for Sunburst, MT

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