Knowing your exact frost dates is the single most important piece of information for any vegetable gardener in the US. Our free calculator uses 30-year historical data from NOAA weather stations to give you reliable last spring frost and first fall frost estimates for your ZIP code.
What Is the Last Frost Date?
Your last spring frost date is the average final date when temperatures in your area drop to 32°F (0°C) or below. This is the benchmark gardeners use to time outdoor planting of frost-sensitive crops like tomatoes, peppers, basil, and cucumbers.
What Is the First Fall Frost Date?
The first fall frost date marks the average day when temperatures first dip to freezing in autumn. This signals the end of the growing season for warm-season crops and tells you when to harvest, protect, or mulch tender plants before they are damaged.
What Is Growing Season Length?
Growing season length is simply the number of frost-free days between your last spring frost and your first fall frost. Most vegetables need 60–120 days. A 150-day season suits everything from radishes to long-season watermelons.
Understanding Frost Probability
Frost dates are expressed as probabilities. A 50% probability date means there is an equal chance of frost before or after that day. Conservative gardeners should use the 10% date (frost very unlikely) while risk-tolerant gardeners may use the 90% date with row covers ready.
Light Frost (28–32°F)
A brief dip to near-freezing. Hardy crops like kale, spinach, and carrots survive — or even taste sweeter. Protect tender seedlings with a light row cover or old bedsheets overnight.
Moderate Freeze (24–28°F)
Wide-ranging damage to most vegetables. Tender annuals will be killed. Root vegetables in the ground are usually fine. This temperature range ends the season for most unprotected crops.
Hard Freeze (Below 24°F)
Severe damage or death of nearly all above-ground vegetation. Only the most cold-hardy plants like overwintering kale and parsnips survive. A hard freeze definitively ends the outdoor growing season.
Use this reference table to understand general frost timing across the continental US. For your precise location, always use the ZIP code calculator above.
🌱 Late Winter — Seed Starting
Count back from your last frost date. Start peppers and eggplant 10–12 weeks before. Tomatoes need 6–8 weeks. Onions and leeks benefit from 10–12 weeks of indoor growing time before transplanting.
🌿 Early Spring — Cold-Hardy Crops
Peas, spinach, kale, and radishes tolerate frost down to 28°F. Direct sow or transplant these 4–6 weeks before your average last frost date for the earliest possible harvest of the season.
☀️ After Last Frost — Warm-Season Planting
Once nighttime lows stay above 50°F and your last frost date has passed, transplant tomatoes, peppers, cucumbers, squash, and basil. Soil temperature of 60°F or above is ideal for most warm-season crops.
🍂 Before First Fall Frost — Season Extension
Watch your first fall frost date closely. Harvest summer crops before the first hard freeze. Extend your season 4–6 weeks with cold frames, row covers, or low tunnels. Fall is ideal for a second planting of cool-season greens.
Frost Date FAQs
What is a frost date?
A frost date is the average calendar date when air temperatures at your location drop to 32°F (0°C). Gardeners track two frost dates each year: the last spring frost, which marks the start of the safe planting window, and the first fall frost, which signals the end of the growing season for warm-weather plants.
How do I find my last frost date by ZIP code?
The fastest way is to use the free ZIP code calculator at the top of this page. It cross-references your location with 30 years of NOAA weather station records and returns your average last spring frost and first fall frost dates within seconds. You can also use the USDA Zone table above for a quick regional estimate.
Can I plant tomatoes before my last frost date?
Tomatoes are frost-sensitive and should not be transplanted outdoors until after your last frost date — and ideally 1–2 weeks after, when nighttime temperatures reliably stay above 50°F. Planting in cold soil stalls growth even if frost does not kill the plant. Start seeds indoors 6–8 weeks before the date shown by this calculator.
What vegetables can be planted before the last frost?
Hardy cool-season vegetables tolerate frost and can be planted 2–6 weeks before your last frost date. These include peas, spinach, kale, Swiss chard, lettuce, broccoli, cabbage, radishes, carrots, beets, and onion sets. Garlic and asparagus crowns go in even earlier in spring or the prior fall.
What is the difference between a light frost and a killing frost?
A light frost occurs when temperatures briefly drop to 28–32°F and typically damages only the most tender plants. A killing frost (sometimes called a hard freeze) occurs at 24°F or below for sustained periods and will destroy essentially all unprotected vegetation above ground. Our calculator shows your 50% probability date for a standard 32°F frost.
How accurate is a frost date calculator?
Frost date calculators are highly useful planning tools but are not guarantees. They express historical probabilities — a 50% date means frost is equally likely on either side. Real-world microclimates, elevation changes, urban heat islands, and year-to-year climate variation can shift your actual frost date by 1–3 weeks. Always monitor your local weather forecast in the days leading up to planting, especially in spring.
How do I extend my growing season past the first frost?
Season extension tools add 4–8 weeks to both ends of your growing season. Low-cost options include lightweight row covers (floating fabric), cold frames made from old window frames and lumber, plastic mulch to warm soil in spring, and thick straw mulch to protect root vegetables in fall. In warmer zones, unheated hoop houses can enable year-round production of cold-hardy greens.
About This Frost Date Calculator
This free tool is designed specifically for home gardeners and small-scale growers in the continental United States. Frost date estimates are derived from 30-year historical climate averages following NOAA methodology, cross-referenced by ZIP code prefix to the nearest representative climate region. The tool returns your average last spring frost, first fall frost, growing season length in days, and a three-probability frost window (10%, 50%, and 90%) to help you make informed decisions at every stage of the gardening season.
For precise seed-starting schedules based on your frost dates, also try our Planting Date Calculator. For planning raised bed volume and soil mix, visit our Raised Bed Soil Calculator.