What USDA hardiness zone is Grimes County, Texas?

Every ZIP code in Grimes County, Texas is USDA hardiness zone 9a, from the USDA 2023 Plant Hardiness Zone Map.

When is the last spring frost in Grimes County, Texas?

The median last spring freeze runs February 27 – March 16 across the 4 NOAA weather stations serving Grimes County, Texas, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Texas

Planting zones in Grimes County, Texas

Every ZIP code in this county is USDA zone 9a — so unlike most of the places people look up, there is one right answer here and it holds wherever you are in the county.

USDA zone 9a The same in all 7 ZIP codes

ZIP codes 7 7 have a NOAA station within range

Weather stations 4 NOAA 1991–2020 normals, across 787 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Grimes County, Texas as a whole. Hardiness zones and freeze dates are published per ZIP code, so yours is exact — enter it and this page will tell you your zone, which NOAA station it comes from and how far away that station is.

The growing season in Grimes County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives November 11 – November 30 across the 4 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around January 2 – January 19 — counted back from a last spring freeze of February 27 – March 16 here.

Every spring date for your ZIP →

These are ranges across the whole county. The ZIP lookup above gives the dates from your own nearest station instead.

All 4 stations agreeAt least one station

Every one of the 4 NOAA stations serving this county counts March 16 – November 11 as growing season (240 days). Widening to any single station gives February 27 – November 30 (276 days).

That is a 36-day difference inside one county — which is why this page gives ranges rather than a single planting date. The ZIP lookup above resolves it to one station.

Your freeze dates

Last spring freeze February 27 – March 16

First fall freeze November 11 – November 30

Across the 4 NOAA stations serving this county. These are medians — half of years freeze later than the date shown — so treat the later end of each range as the cautious one.

The growing season runs 240–278 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 93.7–94.7 °F in June–August. That is past the point where tomato and pepper pollen fails and cool-season greens bolt, so in this county heat decides as much as frost does. Summer rain over the same months runs 9.1–10.6" across those 4 stations, against the rough inch a week — about 13 inches over the same 92 days — that a vegetable garden is usually reckoned to want. The middle station covers about 77% of it, so expect to make up the rest. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 94 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Grimes County

Zones are published per ZIP code, not per county, so this is the exact answer rather than the county's average. The station column is the nearest one to that ZIP code's centroid and how far away it is — the same figure the tools use, shown here so you can see which ZIP codes are well covered and which are reaching.

ZIP code	USDA zone	Nearest NOAA station	Distance
77363	9a	Washington SP, TX	29.7 km
77830	9a	Washington SP, TX	27.9 km
77831	9a	Madisonville, TX	23.1 km
77861	9a	College Stn, TX	28.5 km
77868	9a	Washington SP, TX	11.8 km
77875	9a	Washington SP, TX	35.2 km
77876	9a	Huntsville Muni AP, TX	30.6 km

ZIP-code positions are area centroids, so a large rural ZIP code's listed distance is measured from the middle of its area rather than from any particular address in it.

When to start seeds in Grimes County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 4 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	January 2 – January 19	8 wk before
🌶️ Peppers	Start indoors	January 2 – January 19	8 wk before
🥦 Broccoli	Start indoors	January 16 – February 2	6 wk before
🥬 Cabbage	Start indoors	January 16 – February 2	6 wk before
🥬 Collards	Start indoors	January 16 – February 2	6 wk before
🥬 Kale	Start indoors	January 16 – February 2	6 wk before
🥬 Leaf Lettuce	Start indoors	January 16 – February 2	6 wk before
🫛 Peas	Direct sow	January 16 – February 2	6 wk before
🥬 Spinach	Direct sow	January 16 – February 2	6 wk before
🍠 Sweet Potato	Start indoors	January 16 – February 2	6 wk before
🍅 Tomatoes	Start indoors	January 16 – February 2	6 wk before
🥬 Bok Choy	Start indoors	January 23 – February 9	5 wk before
🥬 Kohlrabi	Start indoors	January 23 – February 9	5 wk before
🥬 Swiss Chard	Start indoors	January 23 – February 9	5 wk before
🥬 Arugula	Direct sow	January 30 – February 16	4 wk before
🥬 Baby Salad Greens	Direct sow	January 30 – February 16	4 wk before
🥕 Beets	Direct sow	January 30 – February 16	4 wk before
🧅 Green Onions	Direct sow	January 30 – February 16	4 wk before
🥬 Mustard Greens	Direct sow	January 30 – February 16	4 wk before
🌶️ Okra	Start indoors	January 30 – February 16	4 wk before
🌱 Radishes	Direct sow	January 30 – February 16	4 wk before
🥔 Turnips	Direct sow	January 30 – February 16	4 wk before
🥬 Cabbage	Set out	February 6 – February 23	3 wk before
🥕 Carrots	Direct sow	February 6 – February 23	3 wk before
🥬 Collards	Direct sow	February 6 – February 23	3 wk before
🥬 Collards	Set out	February 6 – February 23	3 wk before
🥒 Cucumbers	Start indoors	February 6 – February 23	3 wk before
🧅 Green Onions	Set out	February 6 – February 23	3 wk before
🥬 Kale	Direct sow	February 6 – February 23	3 wk before
🥬 Kale	Set out	February 6 – February 23	3 wk before
🥬 Kohlrabi	Direct sow	February 6 – February 23	3 wk before
🥬 Kohlrabi	Set out	February 6 – February 23	3 wk before
🥬 Leaf Lettuce	Direct sow	February 6 – February 23	3 wk before
🎃 Pumpkins	Start indoors	February 6 – February 23	3 wk before
🎃 Summer Squash	Start indoors	February 6 – February 23	3 wk before
🎃 Winter Squash	Start indoors	February 6 – February 23	3 wk before
🥒 Zucchini	Start indoors	February 6 – February 23	3 wk before
🥬 Bok Choy	Direct sow	February 13 – March 2	2 wk before
🥬 Bok Choy	Set out	February 13 – March 2	2 wk before
🥦 Broccoli	Set out	February 13 – March 2	2 wk before
🌿 Cilantro	Direct sow	February 13 – March 2	2 wk before
🥬 Leaf Lettuce	Set out	February 13 – March 2	2 wk before
🥬 Swiss Chard	Direct sow	February 13 – March 2	2 wk before
🥬 Swiss Chard	Set out	February 13 – March 2	2 wk before
🌿 Dill	Direct sow	February 20 – March 9	1 wk before
🫘 Bush Beans	Direct sow	March 6 – March 23	1 wk after
🥒 Cucumbers	Set out	March 6 – March 23	1 wk after
🎃 Pumpkins	Direct sow	March 6 – March 23	1 wk after
🎃 Pumpkins	Set out	March 6 – March 23	1 wk after
🎃 Summer Squash	Direct sow	March 6 – March 23	1 wk after
🎃 Summer Squash	Set out	March 6 – March 23	1 wk after
🌽 Sweet Corn	Direct sow	March 6 – March 23	1 wk after
🍅 Tomatoes	Set out	March 6 – March 23	1 wk after
🎃 Winter Squash	Direct sow	March 6 – March 23	1 wk after
🎃 Winter Squash	Set out	March 6 – March 23	1 wk after
🥒 Zucchini	Direct sow	March 6 – March 23	1 wk after
🥒 Zucchini	Set out	March 6 – March 23	1 wk after
🥒 Cucumbers	Direct sow	March 13 – March 30	2 wk after
🌶️ Okra	Direct sow	March 13 – March 30	2 wk after
🌶️ Okra	Set out	March 13 – March 30	2 wk after
🌶️ Peppers	Set out	March 13 – March 30	2 wk after
🫘 Southern Peas	Direct sow	March 13 – March 30	2 wk after
🍠 Sweet Potato	Set out	March 13 – March 30	2 wk after

Offsets are published guidance; the dates they land on are computed from measured NOAA normals. The seed-starting tool does this for your own ZIP code and counts the days.

What lives through a zone 9a winter

Of 74 perennial edibles, 46 come through a zone 9a winter — and 25 fail here for being too warm rather than too cold, needing more winter chill than this county gets or more heat than they tolerate. Among the ones that work: Elderberry, Horseradish, Sunchoke, Walking Onion, Chives, Mint, American Persimmon, European Plum.

Hardiness ranges are a judgement, published by growers rather than measured; the zone they are compared against is measured. On a warm-end verdict, check with your local extension service — a coastal zone 8 and an inland zone 8 are not the same summer.

Cautious — shortens the seasonMedian across stationsOptimistic

Last spring freeze: Plan to April 7 to be careful. Median February 27 – March 16 across 4 stations; January 31 is the optimistic end.
First fall freeze: Plan to October 25 to be careful. Median November 11 – November 30 across 4 stations; December 26 is the optimistic end.

NOAA publishes these as probabilities, not averages — the middle figure is a median, so half of years fall either side of it. The cautious end is the 10% tail: in roughly nine years in ten the freeze falls on the safe side of it.

The 4 stations behind these numbers

All 4 NOAA stations whose normals this page quotes, spanning about 68 km north to south. Every one is named with its identifier in the station list below — this page does not single one out, because no one station speaks for a whole county.

A relative sketch, not a map with a projection: longitude is adjusted for latitude so the shape is not stretched, and there is no basemap. For the one station nearest a specific address, with its real distance, use the ZIP lookup above.

These are the stations this county's ZIP codes actually cite as nearest — not a claim that each one sits inside its boundary, since a rural ZIP legitimately reaches over it. Every figure above comes from them, and each is named so you can check it.

Station	NOAA ID	Last spring freeze	First fall freeze	Season
College Stn, TX	USW00003904	February 27	November 30	278 days
Huntsville Muni AP, TX	USW00053903	March 2	November 26	272 days
Madisonville, TX	USC00415477	March 16	November 11	240 days
Washington SP, TX	USC00419491	March 7	November 19	259 days

These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.

Your own ZIP

Work out your own dates

This page describes a whole county. Every tool below answers for one ZIP code, which is the grain the underlying data is published at.

Other places to compare

Grimes County sits in Texas. That page carries the whole state's zone spread, its metro areas, and every other county in it with a page here.

More of Texas

Counties with the same zones — 9a

Matched on the exact zone set, not a dominant zone, so the winter answer on these pages really is the same one as here.

Gear

If you want to act on this

Each link opens an Amazon search rather than a product we picked. We have not tested these and do not rank them — the search is the honest version, and you choose.

Shade clothSummer highs here average 94 °F, at or above the 90 °F point where lettuce and spinach bolt and tomato pollen fails.
Row cover and frost clothThe season here closes at the first fall freeze dated above — a cover buys back some of those days at the end.

As an Amazon Associate we earn from qualifying purchases. That costs you nothing extra, and it buys no influence over anything on this site: the dates come from NOAA normals and the zones from the USDA, and no product affects either.

Sources

Where these numbers come from

Hardiness zones are the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. Freeze dates and growing-season lengths are NOAA 1991–2020 Climate Normals, taken per station and cited above by name and NOAA ID.

County boundaries come from the Census ZCTA-to-county relation, which is what places each ZIP code — and which treats parishes, boroughs and census areas as county equivalents. No station is chosen to represent this county: every range above is taken across all of them and the count is stated, because picking one would be a judgement dressed as a measurement.