Austin Frost Dates: When Your Garden Is Safe to Plant

Austin’s Frost Dates: The Numbers That Matter

Austin’s median last frost falls on February 18 at Austin-Bergstrom Airport (USW00013958), but ranges to March 15 at the Mabry station (USW00013904). Your 90% safe planting date spans from March 13 to April 5 depending on your exact location.

This 23-day gap between the median and 90% safe dates reveals why experienced Austin gardeners wait until mid-March for tender crops. The median represents a 50% probability — essentially a coin flip. The 90% safe date gives you much better odds for protecting your tomato and pepper investment.

Your first fall frost typically arrives December 5, creating a 290-day frost-free growing season at the airport location. The shorter 245-day season at Mabry reflects Austin’s microclimatic variation — urban heat island effects and elevation differences create distinct growing zones within the metro area.

Austin sits firmly in USDA Zone 9a (20-25°F minimum temperatures), upgraded from Zone 8b in the 2023 map revision. This warming trend reflects decades of climate data showing fewer extreme cold events and earlier spring warming patterns across Central Texas.

Should You Cover Your Plants Tonight?

Protect your plants when temperatures drop to 35°F or below — frost formation begins before the official 32°F threshold. Tomatoes suffer damage at 33°F, while peppers and eggplant start declining at 35°F. Citrus trees need protection below 28°F, and even cold-hardy vegetables like broccoli benefit from covers below 25°F.

Radiative frost forms on clear, calm nights when heat radiates away from plant surfaces. Row covers, old sheets, or even Christmas lights provide effective protection by trapping ground heat. Advective freezes — driven by cold wind — require more substantial protection like wrapping citrus trunks or moving containers to sheltered locations.

Your frost risk peaks in January and February, with the 10% probability date falling between February 3-18 depending on station location. The 90% safe date means only 1 in 10 years will see frost after March 13-April 5. Use these percentiles to balance risk versus reward — plant early for longer harvests, but accept occasional losses.

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Check overnight lows and wind conditions together. A windy 34°F night causes more damage than a calm 30°F night with good radiative protection.

What Can You Plant After the Last Frost?

Plant tomatoes 2-4 weeks after your 90% safe date — between March 27 and April 19 for most Austin locations. Peppers follow the same schedule, while eggplant needs an additional week of soil warming. These warm-season crops require soil temperatures above 60°F for proper root development.

Squash, cucumbers, and beans can go in the ground 1-2 weeks after the last frost date. Sweet corn needs soil temperatures reaching 65°F consistently — typically early April in Austin. Okra demands the warmest conditions, waiting until mid-April when soil hits 70°F.

Heat-loving crops like melons, sweet potatoes, and Southern peas wait until late April or early May. These crops actually perform better with delayed planting — early sowings often struggle through cool spring weather and get overtaken by properly timed plantings.

Cold-hardy vegetables follow different rules. Plant broccoli, kale, and lettuce 2-4 weeks before your median last frost — late January through early February. These crops tolerate light frost and benefit from cool weather establishment before spring heat arrives.

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Carrots, radishes, and peas can go in the ground 4-6 weeks before the last frost date, taking advantage of Austin’s mild winter conditions for early spring harvests.

Your Fall Planting Window

Work backward from your December 5 first frost date to determine fall planting schedules. Frost-tolerant crops like broccoli (70 days to maturity) need planting by late September. Kale and carrots (55-65 days) can wait until early October, while spinach (40 days) pushes into late October.

Frost-susceptible crops require different calculations. Tomatoes need 75-85 days from transplant to avoid frost damage, meaning final plantings by mid-September. Peppers (70-80 days) follow similar timing, while eggplant (80-90 days) needs August transplanting for fall harvest.

Heat-lovers like okra present the biggest challenge — they need hot weather to grow but must mature before frost. Plant okra by early August for fall production, accepting that September plantings rarely succeed. Southern peas work better, tolerating cooler weather and maturing in 60-70 days from late August sowings.

Cool-season crops actually prefer fall growing conditions over spring. Fall broccoli develops better head formation, while lettuce avoids the bolting pressure of lengthening spring days. Carrots planted in September develop superior sweetness from fall temperature swings.

Time your fall garden to hit peak production in November and December — Austin’s most pleasant outdoor months with minimal pest pressure and optimal growing conditions.

Your Growing Degree Day Calendar

Austin accumulates 6,679 Growing Degree Days (base 50°F) annually, with peak accumulation during summer months. March delivers 306 GDD (5% of annual total), while June provides 931 GDD and August peaks at 1,044 GDD — 16% of the year’s heat units in a single month.

By mid-April, you’ve accumulated approximately 1,060 GDD — sufficient heat for most warm-season crop germination and early growth. Cool-season crops begin growth with minimal GDD accumulation, explaining why February broccoli plantings succeed despite only 103 GDD in January.

Tomatoes require 1,200-1,800 GDD from transplant to first harvest, depending on variety. Austin typically accumulates this amount by late June for April plantings, explaining why properly timed tomatoes produce heavy yields before summer heat stress begins.

Corn needs 2,500-2,700 GDD for maturity — achievable with April plantings reaching harvest by late July. Sweet corn planted too late faces incomplete ear development when fall cooling reduces GDD accumulation rates.

Use GDD accumulation to predict harvest timing and succession planting intervals. Austin’s high summer accumulation rates allow rapid crop turnover during peak season, while spring and fall require longer intervals between plantings.

Your Fruit Tree Compatibility Guide

Austin’s 350 typical chill hours (range: 200-450) support excellent fruit production for properly selected varieties. Low-chill apples like Anna, Dorsett Golden, and Ein Shemer require only 200-300 chill hours — well within Austin’s capacity. Standard varieties needing 800+ hours fail to break dormancy properly.

Avocados thrive in Austin’s Zone 9a climate, with Hass and Fuerte varieties surviving typical winter minimums. Plant in protected locations for insurance against occasional Zone 7-8 events. Bananas produce reliably, dying back to roots during freezes but regrowing vigorously from established plants.

Figs excel in Austin conditions, with Chicago Hardy and Brown Turkey varieties producing two crops annually. Blackberries and Southern highbush blueberries (Sharpblue, Misty, Sunshine Blue) fruit heavily with proper chill hour accumulation.

Muscadine grapes outperform bunch grapes in Austin’s climate, handling summer heat and humidity while requiring minimal chill hours. Dragon fruit grows successfully in containers, moving to protected locations during freeze events.

Avoid high-chill fruit trees entirely — standard peaches, most apples, and sweet cherries waste garden space and investment. Focus on adapted varieties that work with Austin’s climate patterns rather than fighting them.

Time fruit tree planting for late winter — January through early March allows root establishment before summer heat stress begins.

Your Climate Extremes and Planning

Austin experiences occasional Zone 7-8 events despite its Zone 9a classification — Winter Storm Uri in 2021 and the January 2025 freeze demonstrate this variability. Plan for these outlier events by selecting cold-hardy cultivars and maintaining flexible protection strategies.

Cold-hardy vegetables like kale, Brussels sprouts, and carrots survive these extreme events with minimal protection. Perennial herbs like rosemary and thyme need selection of hardier varieties — Arp rosemary survives better than tender Mediterranean types.

Fruit trees benefit from cold-hardy rootstocks and protected planting locations. Citrus trees in containers allow movement to protected areas during extreme events. Established fig trees die back but regenerate from roots after severe freezes.

Summer extremes present equal challenges — temperatures above 100°F for extended periods stress even heat-adapted crops. Provide afternoon shade for cool-season vegetables and maintain consistent soil moisture during heat waves.

Design your garden with both extremes in mind: select diverse varieties, plan protected growing areas, and maintain emergency protection materials for unexpected weather events.

Your Frost Date Comparison Table

The stark difference between stations reflects Austin’s microclimatic diversity. Bergstrom Airport sits in a low-lying area with good cold air drainage, while Mabry experiences more urban heat island effects and elevation protection.

Your specific location likely falls somewhere between these extremes. Properties near Barton Creek or other low-lying areas behave more like Bergstrom, while central Austin locations track closer to Mabry patterns.

Use the conservative Mabry dates if you’re risk-averse with expensive transplants. Use Bergstrom dates if you’re willing to gamble on earlier planting for extended harvest seasons. Track your actual frost dates over several years to refine timing for your specific microclimate.

The 15-day difference in fall frost dates affects late-season gardening significantly. Properties following the Mabry pattern gain two additional weeks of growing season — valuable time for final harvests and extended cool-season production.

Your Monthly Growing Conditions

January’s mild 49.2°F average allows active gardening throughout winter — plant cool-season crops, prune dormant fruit trees, and prepare beds for spring. The 103 GDD accumulation supports slow but steady growth in cold-hardy vegetables.

March marks the transition to serious growing season with 306 GDD — triple January’s accumulation. This rapid temperature increase signals time for spring transplants and direct seeding of warm-season crops.

June and August represent peak growing conditions with maximum GDD accumulation. June’s 931 GDD supports explosive growth, while August’s 1,044 GDD peak requires heat stress management through mulching, shade cloth, and consistent irrigation.

December’s return to 50.4°F temperatures allows continued cool-season production while reducing plant stress. The 119 GDD accumulation maintains growth in established cold-hardy crops while new plantings remain dormant until spring warming begins.

Your Succession Planting Schedule

Austin’s long growing season and rapid GDD accumulation enable multiple succession plantings for extended harvests. Plant lettuce every 2 weeks from February through April, then resume in September through November for continuous salad production.

Bush beans mature in 50-60 days, allowing plantings every 3 weeks from April through August. Time final plantings for early August to mature before October heat stress and potential early frost events.

Carrots require 65-75 days but tolerate both heat and light frost, enabling plantings from February through September. Spring plantings mature in May, while fall plantings develop superior sweetness through winter temperature fluctuations.

Radishes grow quickly (25-30 days) and tolerate temperature extremes, allowing almost year-round production with strategic timing. Plant every 2 weeks except during peak summer heat (July-August).

Sweet corn needs 70-90 days and performs poorly in extreme heat. Plant every 2 weeks from March through May, then skip summer for a final planting in late July for fall harvest.

Time succession plantings using GDD accumulation rather than calendar dates — this accounts for seasonal temperature variations and provides more accurate maturity predictions.

Your Urban Gardening Advantages

Austin’s 284,583 owner-occupied households in Travis County represent substantial garden potential within the metro area’s diverse microclimates. Urban properties benefit from heat island effects that extend growing seasons and reduce freeze risk compared to rural areas.

Buildings provide wind protection and thermal mass — south-facing walls create warm microclimates for heat-loving crops like peppers and tomatoes. North-facing areas offer afternoon shade valuable for cool-season vegetables during Austin’s intense summers.

Container gardening suits urban properties with limited space, allowing movement of tender plants during freeze events and rotation of crops through optimal growing locations. Elevated containers improve drainage during Austin’s occasional heavy rainfall periods.

Vertical growing maximizes production in small spaces — trellises for beans, peas, and cucumbers multiply growing area while improving air circulation. Intensive planting methods work well in Austin’s fertile urban soils and long growing season.

Urban soil temperatures run 5-10°F warmer than rural areas, enabling earlier spring planting and extending fall production. This thermal advantage reduces frost risk and accelerates warm-season crop establishment.

Access to municipal water systems provides irrigation reliability crucial during Austin’s periodic drought conditions and summer heat extremes.

About This Data

Frost date information derives from NOAA’s 1991-2020 Climate Normals, representing 30 years of temperature observations at Austin-Bergstrom International Airport (USW00013958) and Austin Mabry Field (USW00013904). These stations provide the most reliable long-term climate data for the Austin metropolitan area.

Growing Degree Day calculations use the standard base temperature of 50°F, accumulated from daily temperature averages throughout the year. Monthly values represent 30-year averages from the same NOAA dataset.

USDA Plant Hardiness Zone classifications reflect the 2023 map update, incorporating recent climate trends and improved data analysis methods. Zone 9a designation indicates average annual minimum temperatures between 20-25°F.

Chill hour accumulations use the standard below-45°F threshold, calculated from historical temperature records. Fruit tree compatibility recommendations reflect research from Texas A&M AgriLife Extension and variety trials conducted in Central Texas conditions.

Frost probability percentiles indicate the chance of experiencing frost on or after specific dates — 10% means 1 in 10 years will see frost after this date, while 90% safe dates see frost only 1 in 10 years after the specified date.