When to Plant Tomatoes Outdoors: Dates for Where You Live

Plant tomatoes outdoors once the risk of frost has dropped to about one year in ten, nights average at least 50°F and the soil is about 60°F. For most of the US that is three to four weeks after the average last frost: about April 26 in Philadelphia, May 11 in Columbus and May 19 in Minneapolis.

Most guides stop at “after the last frost.” We tested that against NOAA’s 1991–2020 climate normals for 38,123 ZIP codes. In 86% of them, nights reach 50°F only after frost risk has faded, so warm nights, not frost, set the planting date.

Tomato planting dates for 26 US cities

Each plant-out date is the later of two dates: the 10% last-frost date (after it, a 32°F night comes in about one spring in ten) and the day the normal low reaches 50°F. Seed dates are six weeks earlier. Data come from the NOAA station nearest each ZIP code.¹

Valleys, hilltops and gardens far from the station can run a week or more off. For any other ZIP code, look up your frost dates and their odds.

Why “after the last frost” is usually too early

A frost date tells you when tomatoes stop being killed, not when they start growing well. Utah State University Extension notes that fruit does not set when nights fall below 50°F,⁴ and Penn State Extension warns of blossom drop below 55°F.⁵ West Virginia University Extension describes the 55°F limit this way:

Below this temperature, tomatoes experience chilling injury, which can delay their growth

The gap between frost and warm nights is widest on the Pacific coast. Seattle’s 10% frost date is April 1, but its normal low reaches 50°F only on May 20. In Boston the gap is 27 days; in Columbus, four.

How long to wait after your average last frost

Across all 38,123 ZIP codes, the plant-out date falls a median 24 days after the median last frost. Half fall between 21 and 29 days, and fewer than 1% could plant within two weeks. So if you start from the “average” (50%) last-frost date, add three to four weeks, not the one to two weeks many calendars suggest.

Method: frost dates are NOAA’s 32°F spring probabilities; night temperatures are each station’s monthly normal minimum, interpolated day by day. Normals describe a typical year, so a warm or cold spring can shift the window. The methodology page has the details.

Three signals that it is time to plant

• Frost is unlikely. You are past your 10% date and the 10-day forecast shows no night near freezing.
• Nights stay at 50°F or warmer. 55°F is better: the University of Arizona says tomatoes need nights above 55°F to set fruit.⁸
• The soil is about 60°F. WVU and Utah State both use 60°F soil as the cue.^2,4 Check it with a soil thermometer.

How our dates compare with extension advice

We checked the computed dates against extension advice in six states. Most agree within about a week; Ohio State’s central Ohio date is nine days later than ours:

Sources: University of Minnesota Extension,³ WVU Extension,² Ohio State’s Growing Tomatoes in the Home Garden,¹⁷ Penn State,⁵ OSU Extension’s Clackamas County Master Gardeners¹² and the UF/IFAS Florida Vegetable Gardening Guide.⁶ Where your state publishes a date, follow it.

When to plant tomatoes in Florida, Texas and other warm areas

Where frost is rare, plant early enough for fruit to set before summer nights get too warm. UF/IFAS says tomatoes will not set fruit if nighttime temperatures are above 70°F, although cherry tomatoes sometimes keep producing.⁷

Windows: UF/IFAS,⁶ University of Arizona,⁸ UC Master Gardeners¹¹ and Texas A&M AgriLife.¹⁰ The last column is our NOAA calculation; aim to have plants flowering well before it.

Fall tomatoes: count back from the first frost

Texas A&M AgriLife’s rule is to transplant fall tomatoes about 100 days before the first expected frost.⁹

When to start tomato seeds indoors

Count back six weeks from your plant-out date, not your frost date. The University of Minnesota allows five to six weeks; WVU and Utah State give six to eight.^3,2,4 Earlier starts don’t help. Plants started earlier, says the University of Minnesota:

do not necessarily lead to better or earlier harvests

Our guide to when to start seeds indoors has sowing dates for other crops, and the seed-starting guides cover lights and trays.

Planting earlier with protection

Utah State Extension says that with black plastic mulch and row covers, plants can go out several weeks before the last frost date. Vent covers above 80°F, because fruit aborts above 90°F, and wait to add straw or clippings until the soil is warmer than 75°F.⁴

How to transplant tomatoes

1. 1

   Harden plants off

   Starting about 10 days ahead, set plants outside for a few more hours each day. Bring them in at night and on days below 55°F.²

2. 2

   Plant deep

   On a cloudy, calm day or in late afternoon, strip the lowest leaves and bury part of the stem, or lay leggy plants in a trench three to four inches deep.³

   

3. 3

   Stake and water

   Set stakes or cages at planting, then water well. About an inch of water a week is ideal; uneven moisture invites blossom-end rot.³

Running late? See the FAQ below, and check your first-frost odds in our frost and freeze guides. Planting zones won’t give you a date: USDA hardiness zones are based on the average coldest winter night, not spring frost (see planting zone vs frost date).¹³ For more, see our vegetable guides (such as when to plant potatoes), the garden section and the climate data behind these dates.