Houston Frost Dates: Last Spring & First Fall Freeze Guide

Houston’s Frost Dates: Station Variations Matter

Houston’s median last spring frost occurs February 2 at Intercontinental Airport (Station USW00012918) but February 17 at Hobby Airport (Station USW00012960) — a 15-day difference that directly impacts your planting schedule. The 90% safe spring dates show even wider variation: March 5 at IAH versus March 15 at Hobby.

Your first fall frost typically arrives December 19 based on climate normal data from 1991-2020. This creates a frost-free growing season ranging from 293 days at Hobby to 320 days at Intercontinental — among the longest in Texas. Harris County’s 924,703 owner-occupied households can leverage this extended season for multiple crop successions.

The station difference reflects Houston’s size and microclimates. Intercontinental Airport sits 15 miles north and experiences slightly colder temperatures due to its inland location. Your specific garden location within the metropolitan area determines which station better represents your frost risk.

Should You Cover Your Plants Tonight?

Protect tender plants when temperatures drop to 35°F — damage begins before actual frost forms. Tomatoes suffer tissue damage at 32°F, while peppers and eggplant show injury at 35°F. Citrus trees need protection below 28°F, though mature grapefruit can survive brief dips to 25°F.

Radiative frost occurs on clear, calm nights when heat radiates away from plants. Row covers, blankets, or even cardboard boxes trap this escaping heat. Christmas lights strung through citrus trees provide enough warmth during radiative events. Advective freezes bring cold air masses with wind — these require more aggressive protection like wrapping trunks and covering entire canopies.

The 31-day gap between Houston’s median last frost (February 2) and 90% safe date (March 5) explains why experienced gardeners wait for soil temperature stability rather than rushing spring planting. Use soil thermometers to confirm 60°F soil temperature before transplanting warm-season crops.

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What Can You Plant After the Last Frost?

Plant tomatoes 2-4 weeks after your last frost date for best results. With Houston’s February 2 median date, this means late February through early March transplanting. Peppers require warmer soil — wait 4-6 weeks after last frost, typically mid-March. Eggplant needs even more heat: plant 6-8 weeks after last frost in mid to late March.

Sweet corn goes in the ground 2 weeks after last frost when soil reaches 60°F. Plant okra 4 weeks after last frost — it thrives in Houston’s heat and humidity. Squash and cucumbers transplant well 3-4 weeks after last frost, though direct seeding works better in Houston’s quick spring warm-up.

Beans are frost-sensitive but soil temperature matters more than air temperature. Plant bush beans when soil hits 65°F, typically 3-4 weeks after last frost. Lima beans need 70°F soil — wait until April. Your 320-day frost-free season at Intercontinental Airport allows multiple successions of these warm-season crops through summer.

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Your Fall Planting Window

Work backward from Houston’s December 19 first frost date to determine fall planting schedules. Frost-tolerant crops like broccoli (75-85 days to maturity) should be planted by late September for December harvest. Kale and carrots tolerate light frost and can be planted through early October for winter harvest.

Frost-susceptible crops require earlier timing. Tomatoes need 75-85 days — plant determinate varieties by late August for harvest before frost. Peppers require 70-80 days, so transplant by early September. Eggplant (80-90 days) must go in by mid-August to fruit before cold weather.

Heat-loving crops need the earliest fall starts. Okra requires 90+ degree weather to set pods — your last realistic planting window closes by July 15. Summer squash needs consistent warmth for 50-60 days, making August 1 the cutoff date. This backward calculation from your specific first frost date eliminates guesswork in fall garden timing.

Your Zone 9b Climate Reality

Zone 9b designation means minimum temperatures stay between 25-30°F in most winters. Houston was reclassified to Zone 9b in the 2023 USDA Plant Hardiness Zone Map update, reflecting warming trends in the region. But zone ratings only tell half your gardening story — summer heat proves more limiting than winter cold.

Houston accumulates 7,558 Growing Degree Days annually with peak heat in August reaching 84.2°F average. Your real challenge isn’t surviving 25°F minimums but managing crops through 95°F+ summers with high humidity. Cool-season crops like lettuce and spinach struggle in summer heat despite surviving winter cold.

The 250 typical chill hours (range: 100-350) support most fruit tree varieties but limit some apple and stone fruit options. This chill accumulation combined with Zone 9b minimums creates Houston’s unique growing environment — long seasons with intense summer heat rather than traditional four-season gardening patterns.

Your Fruit Tree Options

Houston’s Zone 9b climate and 250 chill hours support exceptional fruit diversity. Citrus thrives here — grapefruit produces reliably with good cold protection. Figs excel in Houston’s heat and rarely suffer winter damage. Southern highbush blueberries fruit well with proper soil acidification.

Tropical fruits flourish in your extended growing season. Avocados survive most winters and fruit consistently. Bananas produce in protected locations, though hard freezes kill above-ground growth. Dragon fruit and guava both thrive in Houston’s heat and survive typical winter lows.

Muscadine grapes perform better than European varieties in Houston’s humid summers. The native muscadines resist Pierce’s disease and other humidity-related problems. Your 320-day frost-free season allows multiple harvests from ever-bearing fruit varieties, making small-space gardens highly productive with proper variety selection.

Your Spring Planting Calendar by Growing Degree Days

Houston accumulates Growing Degree Days faster than most Texas locations due to the urban heat island effect and Gulf proximity. By mid-April, you’ve accumulated approximately 1,437 GDD (base 50°F) — 19% of the annual total. This rapid spring accumulation explains why Houston gardens start earlier than expected for the latitude.

January averages 189 GDD, enough for cool-season growth but insufficient for warm-season germination. March jumps to 420 GDD as soil temperatures rise consistently above 50°F. This March accumulation signals the start of serious warm-season planting windows.

June peaks at 960 GDD while August maintains 1,058 GDD — your highest monthly accumulation. These summer peaks support heat-loving crops like okra, southern peas, and tropical fruits that struggle in cooler climates. Track GDD accumulation rather than calendar dates for precise planting timing in Houston’s variable spring weather.

Understanding Your Frost Risk Percentiles

The 31-day gap between Houston’s median last frost (February 2) and 90% safe date (March 5) represents significant planting risk for impatient gardeners. Median dates mean 50% chance of later frost — coin-flip odds for expensive transplants. The 90% safe date reduces risk to 1-in-10 chance of damaging frost.

Conservative gardeners use the 10% probability date (90% safe) for transplanting tender crops like tomatoes and peppers. Risk-tolerant gardeners split the difference, planting between median and safe dates with protection strategies ready. Commercial growers often use 80% probability dates as economic compromises.

Your specific microclimate shifts these dates by days or weeks. Low-lying areas frost first, while elevated locations and urban heat islands extend the growing season. South-facing slopes protected from north wind can safely plant 1-2 weeks earlier than exposed locations.

Your Two-Season Growing Strategy

Houston’s climate favors two distinct growing seasons rather than continuous year-round gardening. Spring season runs February through May, while fall season spans September through December. Summer heat limits most cool-season crops, while winter occasionally damages heat-lovers.

Spring season starts with cool-season crops in February: broccoli, kale, carrots, and onions. Transition to warm-season planting in March: tomatoes, peppers, and squash. By May, switch to heat-tolerant summer crops: okra, southern peas, and tropical fruits.

Fall season reverses this pattern. August plantings of heat-lovers extend harvest through October. September brings second plantings of spring crops for winter harvest. December may require frost protection but allows continuous harvest of cold-hardy vegetables through February. This two-season approach maximizes Houston’s 320-day frost-free period.

Planning for Outlier Events

Winter Storm Uri in February 2021 brought Zone 7 conditions to Houston, killing even cold-hardy plants and citrus trees. The January 2025 freeze event again demonstrated that occasional extreme weather occurs despite Zone 9b averages. Plan for these outlier events through resilient plant selection and protection infrastructure.

Choose cold-hardy cultivars as insurance against extreme events. Plant citrus in containers for easy protection. Establish diverse plantings so single events don’t eliminate entire gardens. Build permanent cold frames or have row covers ready for emergency deployment.

View outlier events as opportunities to strengthen your garden’s resilience. Replace plants that died in extreme cold with hardier alternatives. Install permanent protection systems for valuable perennials. These investments pay dividends during the next inevitable extreme weather event.

About This Data

Frost date statistics derive from NOAA’s 1991-2020 climate normal period for Houston weather stations USW00012918 (Intercontinental Airport) and USW00012960 (Hobby Airport). These 30-year averages provide statistically reliable planning baselines while reflecting recent climate trends.

Plant hardiness zone data comes from the 2023 USDA Plant Hardiness Zone Map update. Growing Degree Day calculations use base temperature 50°F standard for general crop development. Chill hour accumulation uses the standard model for fruit tree dormancy requirements.

Fruit tree compatibility assessments combine zone hardiness ratings with chill hour requirements and regional performance trials. Demographic data comes from the U.S. Census Bureau’s American Community Survey 5-year estimates. All temperature and date references reflect 1991-2020 climate normal period unless otherwise specified.