Growli frost calendar — 2026 forecast
First frost date by USDA hardiness zone
— 2026 forecast
What is the first frost date?
The first frost date is the average night each fall when the temperature drops to 32°F (0°C) or below, killing tender warm-season plants. It's an average — about half the years your first frost arrives earlier, half later — but it's the single most useful planning anchor for ending the growing season, planting fall crops, and protecting tender perennials.
How to use this table
Find your USDA zone in the first column. The "average first frost" column is your planning anchor — assume tender crops are done that week. The "crops at risk" column flags which plants will die on the first frost night so you know what to harvest or cover. Click any zone for the full local growing calendar.
First frost date by USDA zone — full table
| Zone | Temperature range | Average first frost | Last spring frost (for context) | Crops at risk on first frost | Zone page |
|---|---|---|---|---|---|
| Zone 1 | -60 to -50°F -51 to -46°C | mid-August | mid-June | Potatoes, peas, cabbage finals — most warm-season crops are already done | Zone 1 → |
| Zone 2 | -50 to -40°F -46 to -40°C | late August | early June | Late potatoes, kale, cabbage, hardy lettuce — pull tender herbs | Zone 2 → |
| Zone 3 | -40 to -30°F -40 to -34°C | early September | late May | Tomatoes, squash, beans, basil — short-season tomato varieties finishing | Zone 3 → |
| Zone 4 | -30 to -20°F -34 to -29°C | mid-September | mid-May | Tomatoes, peppers, basil, summer squash, beans, cucumbers | Zone 4 → |
| Zone 5 | -20 to -10°F -29 to -23°C | late September / early October | late April / early May | Tomatoes, peppers, eggplant, basil, beans, melons, sweet corn | Zone 5 → |
| Zone 6 | -10 to 0°F -23 to -18°C | mid- to late October | mid- to late April | Tomatoes, peppers, eggplant, basil, beans, cucumbers, summer squash | Zone 6 → |
| Zone 7 | 0 to 10°F -18 to -12°C | late October / early November | mid-April | Tomatoes, peppers, basil, sweet potatoes (harvest before), okra | Zone 7 → |
| Zone 8 | 10 to 20°F -12 to -7°C | mid-November | mid- to late March | Late tomatoes, basil, sweet potatoes, peppers, citrus (light frost protection) | Zone 8 → |
| Zone 9 | 20 to 30°F -7 to -1°C | late November / early December | mid-February to early March | Tropical herbs, basil, tender ornamentals — true frost is uncommon and brief | Zone 9 → |
| Zone 10 | 30 to 40°F -1 to 4°C | frost rare or never | frost rare or never | Frost is rare — only the coldest inland nights threaten tender tropicals | Zone 10 → |
| Zone 11 | 40 to 50°F 4 to 10°C | no frost | no frost | No outdoor frost — bring tender potted plants in only during exceptional cold snaps | Zone 11 → |
| Zone 12 | 50 to 60°F 10 to 16°C | no frost | no frost | No frost — heat tolerance is the constraint, not cold | Zone 12 → |
| Zone 13 | 60 to 70°F 16 to 21°C | no frost | no frost | No frost — heat tolerance is the constraint, not cold | Zone 13 → |
Frost-date averages: NOAA Climate Data Online national averages. Local ZIP-code-precise dates can vary by 2–3 weeks from these zone midpoints.
Don't know your zone?
The frost-date table is most useful once you know which row applies to you. Use the Growli zone finder to look up your USDA zone (or UK RHS rating) from your ZIP code or postcode in seconds.
Why first frost matters more than the calendar date
Two gardens 50 miles apart can have first frost dates two weeks apart. Elevation, proximity to large bodies of water, urban heat-island effects, and local cold-air drainage all shift the date from the zone average. Your own backyard microclimate matters too — a south-facing wall, a paved patio, or a canopy of trees can buy you another week.
Treat the average as a planning anchor, not a deadline. Watch the 10-day forecast starting two weeks before your average date, and have row covers or sheets ready to throw over tender crops the night the forecast drops below 38°F (3°C) with clear skies and calm winds — those are the classic frost-night ingredients.
Hardiness zone vs frost date — what each one tells you
They're related but not the same. A hardiness zone describes the average annual minimum winter temperature — useful for picking perennials, shrubs, and trees that will survive your coldest winter night. A frost date describes the average first night below freezing in fall (or the last in spring) — useful for timing annuals, vegetables, and tender crops.
- Hardiness zone answers: will this plant survive winter here?
- First frost date answers: when does my tomato crop end?
- Last frost date answers: when can I plant out tender seedlings in spring?
How to protect plants from the first frost
A single light frost (29–32°F / -2 to 0°C) is survivable for many crops with simple protection. A hard freeze (below 28°F / -2°C) ends the season for almost everything tender. The standard playbook:
- Watch the forecast 10–14 days ahead of your average first frost. The first frost rarely arrives without warning — clear skies, calm winds, and lows near 38°F (3°C) are the signal.
- Harvest fully ripe tender crops the day before. Tomatoes, peppers, basil, beans, summer squash. Green tomatoes can ripen indoors; once frosted they turn to mush.
- Cover what stays in the ground. Row covers, old bedsheets, or frost cloth draped to the ground (not just on top of plants) trap soil heat overnight. Remove covers in the morning when temperatures rise above freezing.
- Water in advance. Moist soil holds and releases heat better than dry soil — water deeply the morning before a forecast frost night.
- Pot up tender herbs. Basil, lemongrass, and tropical herbs can be brought indoors for a second life as houseplants through winter.
Frost vs freeze vs hard freeze — the differences
The National Weather Service uses three distinct terms, and they trigger different protective actions:
| Event | Temperature | What happens | What to do |
|---|---|---|---|
| Light frost | 29–32°F (-2 to 0°C) | Ice forms on leaf surfaces. Tender annuals (basil, beans) die; tomatoes get damaged but may survive. | Cover tender plants with row cover or sheet. Harvest ripe tomatoes and peppers. |
| Freeze | 25–28°F (-4 to -2°C) | Soft cells rupture. Almost all warm-season crops finish for the year. | Pull all warm-season plants. Mulch perennials and garlic. Bring tropicals indoors. |
| Hard freeze | Below 25°F (below -4°C) | Soil begins to freeze. Even hardy crops (kale, leeks) need protection or harvest. | Harvest remaining brassicas and root crops. Mulch deeply. Drain irrigation lines. |
UK gardeners — how this compares to RHS hardiness
The UK doesn't use USDA zones — the Royal Horticultural Society uses an H1–H7 plant-by-plant hardiness rating instead. For first frost dates, the practical UK average is mid-October to early November across England and Wales, mid- to late October in Scotland and high elevation, and rarely before mid-November on the southwest coast. The Growli UK zones page translates each RHS band into US-equivalent guidance.
Get frost alerts from Growli
The frost dates above are averages. Your actual first frost depends on the 10-day weather forecast and your specific microclimate — and you don't want to discover frost is coming the morning after your tomatoes died. Growli sends a push notification 24–48 hours ahead of any forecast frost night for your saved location, tied to local National Weather Service (US) or Met Office (UK) data.