Zone 3 planting calendar
Typical frost dates for USDA hardiness zone 3, and a month-by-month table of when to start seeds and plant out. Your own dates depend on your location within the zone, so use these as a starting point.
Zone 3 at a glance
From NOAA 1991–2020 climate normals for 3 example stations in zone 3 (32°F threshold, 50% probability).
Zone 3 is about winter cold, not spring frost
The USDA Plant Hardiness Zone Map divides the country by the average coldest winter night: each zone covers 10°F, and the "a" and "b" halves cover 5°F each. Zone 3 is the right guide for choosing perennials that survive the winter. It is only a rough guide to planting dates, because places with similar winter lows can have very different springs. That is why this page gives a range of frost dates rather than a single date, and why the frost date for your own location is a better input for the seed starting calculator.
Zone 3 combines very cold winters with a short frost-free season, so most of the work here is about time. Long-season crops such as peppers, eggplant and melons need an indoor start and early-maturing varieties, and even then a cool summer can leave them short. Cool-season crops like lettuce, spinach, kale, cabbage and onions are the reliable core of a zone 3 garden. Row covers and black plastic mulch, both recommended by University of Minnesota Extension for warming soil and protecting young plants, earn their keep here.
Typical frost dates in zone 3
The table lists example cities whose airport or city weather station falls in zone 3. "Last frost" is the date after which a 32°F freeze has a 50% chance of still happening; the "1-in-10" column is the date after which there is only a 10% chance. Planting tender crops after the 1-in-10 date is the cautious choice.
| City (station) | Zone | Last frost (median) | Last frost (1-in-10 later) | First fall frost (median) | Freeze-free days |
|---|---|---|---|---|---|
| Fairbanks, AK | 3b | May 13 | May 26 | Sep 13 | 121 |
| Havre, MT | 3b | May 15 | May 27 | Sep 23 | 129 |
| International Falls, MN | 3b | May 29 | Jun 16 | Sep 13 | 109 |
Zone shown is the 2023 USDA zone for the ZIP code nearest each weather station, via PRISM data. Frost dates are NOAA 1991–2020 normals for that station. Dates for nearby gardens can differ by a week or more with elevation, slope and distance from water. Find your own station on NOAA's map (see how to find your frost dates).
Month by month: what to start when in zone 3
This table uses the middle example above, Havre, MT (median last frost May 15), and the University of New Hampshire Extension seed-starting timings. If your last frost is a week later, move everything a week later.
| Month | Start seeds indoors | Plant transplants out | Direct sowing reminders |
|---|---|---|---|
| February | Onions (Feb 6–Feb 20) Parsley (Feb 13–Feb 20) Spinach (Feb 20–Mar 6) | — | — |
| March | Broccoli (Mar 6–Mar 20) Cabbage (Mar 6–Mar 20) Kale (Mar 6–Mar 20) Lettuce (Mar 13–Mar 20) Peppers (Mar 20–Apr 3) Eggplant (Mar 20–Apr 3) Cauliflower (Mar 20–Apr 3) Tomatoes (Mar 27–Apr 10) | — | — |
| April | Basil (Apr 3–Apr 17) Cucumbers (Apr 24–May 1) | Spinach (Apr 3–Apr 24) Broccoli (Apr 17–May 1) Cabbage (Apr 17) Lettuce (Apr 17–Apr 24) Kale (Apr 17) Onions (Apr 17) Parsley (Apr 24–May 1) | Spinach, lettuce, kale: direct sow once the soil can be worked (see guides) |
| May | Squash & zucchini (May 1–May 8) Melons (May 1–May 8) | Cauliflower (May 1) Tomatoes (May 22–May 29) Cucumbers (May 22–May 29) Peppers (May 29) Eggplant (May 29–Jun 5) Squash & zucchini (May 29) Melons (May 29) Basil (May 29) | Cucumbers, squash: direct sow once soil reaches 70°F, usually after this date Melons: direct sow or transplant once soil is at least 65°F |
Open this schedule in the calculator
Direct-sowing reminders follow the soil-temperature rules in each crop guide (for example, 70°F soil for cucumbers and squash), so the real date depends on your weather. For fall crops, count back from your first fall frost with the fall planting calculator.
Crop guides
Frequently asked questions
When is the last frost in zone 3?
It depends on where you are in the zone. Among the 3 example weather stations on this page, the median last spring freeze (32°F, 1991–2020 NOAA normals) ranges from May 13 to May 29. Look up the station nearest you for a better estimate.
When should I start tomato seeds in zone 3?
For the middle example on this page (last frost May 15, Havre, MT), the University of New Hampshire Extension timing gives an indoor sowing window of Mar 27–Apr 10 and setting out May 22–May 29. Shift those dates by the difference between your own last frost date and May 15.
Is my hardiness zone the same as my frost date?
No. USDA hardiness zones are based on the average annual extreme minimum winter temperature. They tell you which perennials survive winter, not when spring frosts end, which is why frost dates vary so much within one zone.
Sources
- USDA ARS — Plant Hardiness Zone Map
- PRISM Climate Group, Oregon State University — USDA Plant Hardiness Zone Map data (2023); ZIP lookups via phzmapi.org (not the official USDA map)
- NOAA NCEI — U.S. Climate Normals (1991–2020), incl. interactive map with frost/freeze dates
- University of New Hampshire Extension — Growing Vegetables: When to Plant Your Vegetable Garden
Station data retrieved from NOAA NCEI on 22 Oct 2026. Last reviewed 2026-10-23. Found an error? Tell us.