Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 77837 — Calvert, TX

ZIP code 77837 (Calvert, Robertson County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is February 28 and the first fall frost November 28.

Where ZIP 77837 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone9a20 to 25 °F

Coldest night−6.7 to −3.9 °C

Last frostFeb 28

First frostNov 28

2012 zone8b

Was 8b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Calvert, TX…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Calvert, TX

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostFebruary 28median — 50% chance of a later frost

Safe for tender plantsMarch 21only 10% chance of frost after

First fall frostNovember 28median — 10% chance by Nov 6

Growing season277 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 6 and returns around December 14.

From the NOAA station Franklin, TX — 11 miles away, elevation 466 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 77837

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Jan 17 – Jan 31

SpinachSow outdoors · Jan 17 – Feb 7

Broccoli, cabbageStart indoors · Dec 20 – Jan 3

Broccoli, cabbageTransplant · Feb 7 – Feb 21

Onion setsPlant outdoors · Jan 31 – Feb 14

PotatoesPlant outdoors · Feb 7 – Feb 21

LettuceSow outdoors · Jan 31 – Feb 14

Carrots, beetsSow outdoors · Feb 7 – Feb 21

TomatoesStart indoors · Jan 3 – Jan 17

TomatoesTransplant · Mar 7 – Mar 21

Peppers, eggplantStart indoors · Dec 20 – Jan 3

Peppers, eggplantTransplant · Mar 14 – Mar 28

BeansSow outdoors · Mar 7 – Mar 21

Sweet cornSow outdoors · Mar 7 – Mar 21

Cucumbers, squashSow outdoors · Mar 7 – Mar 21

Fall lettuce, spinachSow outdoors · Oct 3 – Oct 17

GarlicPlant cloves · Nov 14 – Dec 19

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 28) and first fall frost (Nov 28) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 77837 came on Jan 30 — about the same time as the 1991–2020 average (Jan 28).

average
Jan 282026
Jan 30

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 9a in Texas

640 plants native to the lower 48 states, recorded in Texas, and rated by the USDA to survive 20 °F or colder — the bottom of zone 9a. Each links to its USDA PLANTS profile.

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Calvert, TX.

Soil in Calvert, TX

The soil mapped at the center of ZIP 77837 is Robco — loamy fine sand, moderately well drained.

TextureLoamy fine sanddrains and warms fast; dries out and needs more feeding

pH5.8moderately acidic; most vegetables like 6.0–7.0

DrainageModerately well drainednatural drainage class

Organic matter0.75%low — add compost

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Robco-Tanglewood complex, 1 to 5 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 77837; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Calvert, TX

Summer high96 °Faverage high, August

Winter low39 °Faverage low, January

Hot days99days a year at 90 °F or more

Freezing nights24nights a year at 32 °F or less

Growing degree days6,897base 50 °F — the season’s usable heat

Longest day14 h 10 mindaylight on June 21

Shortest day10 h 08 mindaylight on December 21

Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb

Precipitation40.5 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Franklin, TX (11 mi away); precipitation: Bremond, TX (10 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

2 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

New Baden, TX · 15 mi

Texas planting zones →

Questions about 77837

What planting zone is ZIP code 77837?

ZIP code 77837 (Calvert, TX) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

When is the last frost in Calvert, TX?

The median last spring frost (32 °F) near 77837 is February 28; after March 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Franklin station.

When is the first frost in Calvert, TX?

The median first fall frost near 77837 is November 28, giving a median frost-free growing season of 277 days.

When should I plant tomatoes in 77837?

Start tomato seeds indoors around Jan 3 – Jan 17 and set transplants outside around Mar 7 – Mar 21, one to three weeks after the median last frost.

How much rain and snow does 77837 get?

About 40.5 inches of precipitation a year (NOAA 1991–2020 normals, Bremond station).

How hot do summers get in Calvert, TX?

The average high peaks at 96 °F in August, with about 99 days a year at 90 °F or more.

What kind of soil does 77837 have?

The USDA soil survey maps Robco at the center of ZIP 77837: loamy fine sand, moderately well drained, pH about 5.8 (moderately acidic).

Did spring come early in Calvert, TX in 2026?

Spring leaf-out near 77837 came on Jan 30 in 2026, about the same as the 1991–2020 average (Jan 28), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Calvert, TX?

Short-day onions: the longest day near 77837 is 14 h 10 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.

Did the zone for 77837 change?

Yes. The 2012 USDA map put 77837 in zone 8b; the 2023 map puts it in zone 9a. The newer map uses 1991–2020 data and more weather stations.