Frost Date Calculator

Find your average first and last frost dates, growing season length, and USDA plant hardiness zone. Select your state below to get started with frost date planning for your garden.

Find Frost Dates by State

Click any state below to view frost dates, hardiness zones, and planting calendars for cities in that state.

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What Are Frost Dates and Why Do They Matter?

Frost dates are among the most critical pieces of information every gardener needs to know. The last spring frost date tells you the average date when overnight temperatures stop dropping below 32 degrees Fahrenheit (0 degrees Celsius) in spring, signaling when it is generally safe to transplant tender seedlings outdoors. The first fall frost date marks the average date when temperatures first dip below freezing in autumn, ending the outdoor growing season for frost-sensitive plants. The span between these two dates determines your growing season length, which dictates which crops you can successfully grow to maturity.

Understanding frost dates helps you plan every aspect of your garden calendar. You will know when to start seeds indoors, when to harden off transplants, when to direct sow warm-season crops like tomatoes and peppers, and when to get your fall harvest in before the cold arrives. Gardeners who ignore frost dates risk losing transplants to a late spring freeze or watching mature plants die before fruits ripen in autumn. Even experienced growers check frost date averages each year because microclimates, elevation changes, and urban heat islands can shift actual freeze events by days or even weeks compared to regional averages.

Our calculator covers more than 200 cities across all 50 states, providing average last spring frost dates, first fall frost dates, growing season length in days, USDA hardiness zones, minimum winter temperatures, and recommended planting windows. Whether you are a beginner planning your first raised bed or a seasoned market gardener scheduling succession plantings, these frost date lookups give you the baseline timing you need to garden with confidence.

Understanding USDA Plant Hardiness Zones

The USDA Plant Hardiness Zone Map divides North America into 13 primary zones based on average annual extreme minimum winter temperatures. Each zone spans a 10-degree Fahrenheit range and is further split into "a" and "b" subzones covering 5-degree ranges. Zone 1a, the coldest, experiences minimum temperatures of negative 60 to negative 55 degrees Fahrenheit, while zone 13b, the warmest, stays above 65 degrees Fahrenheit year-round. Your hardiness zone determines which perennial plants, shrubs, and trees can survive winter in your area without protection.

Frost dates and hardiness zones are related but distinct measurements. Hardiness zones reflect the coldest winter temperature a location typically experiences, which matters for perennial survival. Frost dates, on the other hand, track the timing of the last and first freezes, which matters for annual vegetable and flower gardening schedules. A city might be in zone 7b with mild winters but still have a relatively late last frost in mid-April due to its inland location and elevation. Checking both your zone and your frost dates gives you the complete picture for planning both perennial landscapes and annual vegetable gardens.

View all USDA hardiness zones with temperature ranges and planting recommendations.

How to Use This Frost Date Calculator

Step 1: Find Your State

Select your state from the list above. Each state page shows frost dates for multiple representative cities, covering different climate regions within the state.

Step 2: Find Your City

Click on the city closest to your garden location. If your exact city is not listed, choose the nearest one with a similar elevation and geographic setting.

Step 3: Check Your Planting Window

Each city page shows recommended dates for starting seeds indoors, transplanting outdoors, and the last date for direct sowing fall crops.

Step 4: Know Your Zone

Your USDA hardiness zone tells you which perennial plants can survive winter in your area. Use this when selecting trees, shrubs, and perennial flowers.

Frequently Asked Questions About Frost Dates

What is the difference between a frost and a freeze?

A frost occurs when surface temperatures drop to 32 degrees Fahrenheit or below, forming ice crystals on exposed surfaces. A light frost (29 to 32 degrees Fahrenheit) damages tender plants but leaves cold-hardy crops unharmed. A hard freeze (below 28 degrees Fahrenheit) damages most unprotected garden plants and can kill even semi-hardy vegetables. When planning your garden, pay attention to whether forecasts predict a light frost or a hard freeze, as the distinction affects which crops need protection and which will survive without intervention.

How accurate are average frost dates?

Average frost dates represent the midpoint of historical data, meaning the actual last spring frost or first fall frost can vary by two to three weeks in either direction in any given year. In roughly half of all years, the last frost comes after the average date. Most gardeners add a safety margin of one to two weeks after the average last frost date before transplanting sensitive crops like tomatoes and peppers. Checking local weather forecasts as the date approaches gives you the best protection against unexpected late freezes.

Can I extend my growing season beyond the frost dates?

Absolutely. Season extension techniques include using row covers, cold frames, hoop houses, and unheated greenhouses to protect plants from frost. Row covers made of spun polyester fabric can protect plants from temperatures down to about 28 degrees Fahrenheit. Cold frames add another five to ten degrees of protection. These methods let you transplant two to four weeks earlier in spring and harvest two to six weeks later in fall, significantly extending your effective growing season beyond what the bare frost dates suggest.

Why are frost dates different for cities in the same state?

Frost dates vary within a state because of differences in elevation, proximity to large bodies of water, latitude, and urban heat island effects. A mountain city at 5,000 feet elevation will have a much later last spring frost and earlier first fall frost than a coastal city at sea level in the same state. For example, in Arizona, Phoenix at 1,086 feet experiences its last frost in late January, while Flagstaff at 6,910 feet does not see its last frost until early June. Always use frost data for the city closest to your specific location rather than relying on statewide averages.

What is a growing season and how is it calculated?

The growing season is the number of frost-free days between your average last spring frost and your average first fall frost. It tells you how many days warm-season crops have to grow from transplant to harvest. For example, if your last spring frost is May 4 and your first fall frost is October 4, you have a 153-day growing season. When choosing vegetable varieties, compare the "days to maturity" listed on seed packets to your growing season length. If a tomato variety needs 85 days to maturity and your season is 153 days, you have ample time. If it needs 120 days and your season is only 110 days, you will need to start it indoors early or choose a shorter-season variety.