Place guide
Planting zones in Napa, CA
This metro spans USDA zones 9a to 9b, so there is no single zone for Napa, CA and anyone who gives you one is rounding. 90% of its ZIP codes are zone 9b; the rest are not.
Your ZIP code
Get the exact answer for your address
Everything above describes Napa, CA 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.
Napa, CA does not have one planting answer
Its own weather stations disagree about 19 of the 32 crops in this table right now, so any single list would be wrong for part of the metro area. That is not a gap in the data — it is what the data says.
- Shortest season
- 245 days
ANGWIN PACIFIC UNION COLLEGE, CA US (USC00040212) - Longest season
- 306 days
SAINT HELENA, CA US (USC00047643)
61 days of growing season separate those two stations, and both serve ZIP codes in Napa, CA. The ZIP lookup above answers for one address instead of averaging a place that has no average.
Why the hardiness zone does not settle this
A USDA zone is a winter-minimum statistic. It was never a growing-season one, and it does not behave like one: within a single zone the growing season runs a median 54 days wider at the 10th–90th percentile, and annual growing degree days vary by 2.02×.
The zones also overlap rather than stack — 30% of zone 6b freezes before the median zone 6a station. The zone tells you what survives your winter; the station tells you what finishes before your autumn.
All 6 stations agreeAt least one station
Every one of the 6 NOAA stations serving this metro area counts April 7 – November 21 as growing season (228 days). Widening to any single station gives February 3 – December 5 (305 days).
That is a 77-day difference inside one metro area — which is why this page gives ranges rather than a single planting date. The ZIP lookup above resolves it to one station.
Which zone you are in depends where you are
Napa, CA covers 2 hardiness zones. A guide that gives the metro one zone has picked whichever is largest and rounded everyone else into it — which is fine for the 90% in zone 9b and wrong for the other 10%. Here is the actual split.
| Zone | ZIP codes | Share | |
|---|---|---|---|
| 9b | 9 | 90% | |
| 9a | 1 | 10% |
Zones are published per ZIP code, so yours is exact even though the metro's is not. The hardiness tool will tell you which one you are in.
Your freeze dates
Those are the earliest and latest medians among the 6 stations serving this metro — not an average, and not one station standing in for the rest. Half of years freeze later than a station's own median.
The spread is the point. Even in a metro that is one hardiness zone throughout, its stations disagree about the last spring freeze. Hardiness zone and frost date measure different things — a zone is the average annual coldest night, a freeze date is when the season turns — and a place can be uniform in one and varied in the other. Use the tools below with your own ZIP rather than the ends of this range.
Your growing season
NOAA publishes a growing-season length for each station, and across the 6 stations serving Napa, CA it runs 245–306 days . That figure is published, not computed from the two freeze dates — subtracting one from the other gives the wrong answer wherever a season crosses New Year. Mean summer high (June–August) runs 79–92 °F , at or above the 90 °F point where cool-season crops bolt and tomato and pepper pollen fails — so midsummer sowings of lettuce and its relatives are worth holding here. Summer rain over the same months runs 0.3–0.4" across those 6 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 3% of it, so a summer garden here is watered rather than rained on. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 85 °F summer afternoon drying the soil faster than a cool one.
When to start seeds in Napa, CA
Every spring job for 63 crop dates, counted from this metro's own last spring freeze. Each is a range across all 6 stations — the earliest and latest that job falls anywhere in the metro — because no one station speaks for the whole area.
| Crop | Job | When | Offset |
|---|---|---|---|
| Broccoli | Start indoors | January 1 – December 23 | 6 weeks before |
| Cabbage | Start indoors | January 1 – December 23 | 6 weeks before |
| Collards | Start indoors | January 1 – December 23 | 6 weeks before |
| Kale | Start indoors | January 1 – December 23 | 6 weeks before |
| Leaf Lettuce | Start indoors | January 1 – December 23 | 6 weeks before |
| Peas | Direct sow | January 1 – December 23 | 6 weeks before |
| Spinach | Direct sow | January 1 – December 23 | 6 weeks before |
| Sweet Potato | Start indoors | January 1 – December 23 | 6 weeks before |
| Tomatoes | Start indoors | January 1 – December 23 | 6 weeks before |
| Green Onions | Start indoors | January 5 – December 18 | 8 weeks before |
| Peppers | Start indoors | January 5 – December 18 | 8 weeks before |
| Arugula | Direct sow | January 6 – March 10 | 4 weeks before |
| Baby Salad Greens | Direct sow | January 6 – March 10 | 4 weeks before |
| Beets | Direct sow | January 6 – March 10 | 4 weeks before |
| Green Onions | Direct sow | January 6 – March 10 | 4 weeks before |
| Mustard Greens | Direct sow | January 6 – March 10 | 4 weeks before |
| Okra | Start indoors | January 6 – March 10 | 4 weeks before |
| Radishes | Direct sow | January 6 – March 10 | 4 weeks before |
| Turnips | Direct sow | January 6 – March 10 | 4 weeks before |
| Bok Choy | Start indoors | January 8 – December 30 | 5 weeks before |
| Kohlrabi | Start indoors | January 8 – December 30 | 5 weeks before |
| Swiss Chard | Start indoors | January 8 – December 30 | 5 weeks before |
| Cabbage | Set out | January 13 – March 17 | 3 weeks before |
| Carrots | Direct sow | January 13 – March 17 | 3 weeks before |
| Collards | Direct sow | January 13 – March 17 | 3 weeks before |
| Collards | Set out | January 13 – March 17 | 3 weeks before |
| Cucumbers | Start indoors | January 13 – March 17 | 3 weeks before |
| Green Onions | Set out | January 13 – March 17 | 3 weeks before |
| Kale | Direct sow | January 13 – March 17 | 3 weeks before |
| Kale | Set out | January 13 – March 17 | 3 weeks before |
| Kohlrabi | Direct sow | January 13 – March 17 | 3 weeks before |
| Kohlrabi | Set out | January 13 – March 17 | 3 weeks before |
| Leaf Lettuce | Direct sow | January 13 – March 17 | 3 weeks before |
| Pumpkins | Start indoors | January 13 – March 17 | 3 weeks before |
| Summer Squash | Start indoors | January 13 – March 17 | 3 weeks before |
| Winter Squash | Start indoors | January 13 – March 17 | 3 weeks before |
| Zucchini | Start indoors | January 13 – March 17 | 3 weeks before |
| Bok Choy | Direct sow | January 20 – March 24 | 2 weeks before |
| Bok Choy | Set out | January 20 – March 24 | 2 weeks before |
| Broccoli | Set out | January 20 – March 24 | 2 weeks before |
| Cilantro | Direct sow | January 20 – March 24 | 2 weeks before |
| Leaf Lettuce | Set out | January 20 – March 24 | 2 weeks before |
| Swiss Chard | Direct sow | January 20 – March 24 | 2 weeks before |
| Swiss Chard | Set out | January 20 – March 24 | 2 weeks before |
| Dill | Direct sow | January 27 – March 31 | 1 week before |
| Bush Beans | Direct sow | February 10 – April 14 | 1 week after |
| Cucumbers | Set out | February 10 – April 14 | 1 week after |
| Pumpkins | Direct sow | February 10 – April 14 | 1 week after |
| Pumpkins | Set out | February 10 – April 14 | 1 week after |
| Summer Squash | Direct sow | February 10 – April 14 | 1 week after |
| Summer Squash | Set out | February 10 – April 14 | 1 week after |
| Sweet Corn | Direct sow | February 10 – April 14 | 1 week after |
| Tomatoes | Set out | February 10 – April 14 | 1 week after |
| Winter Squash | Direct sow | February 10 – April 14 | 1 week after |
| Winter Squash | Set out | February 10 – April 14 | 1 week after |
| Zucchini | Direct sow | February 10 – April 14 | 1 week after |
| Zucchini | Set out | February 10 – April 14 | 1 week after |
| Cucumbers | Direct sow | February 17 – April 21 | 2 weeks after |
| Okra | Direct sow | February 17 – April 21 | 2 weeks after |
| Okra | Set out | February 17 – April 21 | 2 weeks after |
| Peppers | Set out | February 17 – April 21 | 2 weeks after |
| Southern Peas | Direct sow | February 17 – April 21 | 2 weeks after |
| Sweet Potato | Set out | February 17 – April 21 | 2 weeks after |
The week offsets are conventional extension guidance and vary by variety; the freeze dates they are counted from are measured. For a single date rather than a range, run when do I start my seeds? with your own ZIP code.
What survives the winter changes across Napa, CA
Of 74 perennial fruits, nuts, berries, vegetables and herbs, 46 come through the winter in zone 9a and only 40 in zone 9b. That is a different garden at each end of the same metro.
| Zone | ZIPs | Survive | Fail for being too warm |
|---|---|---|---|
| 9a | 1 | 46 of 74 | 25 |
| 9b | 9 | 40 of 74 | 32 |
The last column is the counterintuitive one, and it is why the totals do not simply rise as the winters get milder. Most temperate fruit needs a documented number of hours below about 45 °F to break dormancy and set a crop, so an apple fails in a winter that is too warm; currants and rhubarb cook in the summer heat that comes with it. See the full list with reasons.
At least one station here freezes across the new year, which puts the two ends of a spread on opposite sides of the calendar. Drawing it would produce a bar spanning almost the whole year and meaning nothing, so none is drawn.
The 6 stations behind these numbers
All 6 NOAA stations whose normals this page quotes, spanning about 40 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 metro area.
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.
Every figure above comes from these, and each is named so you can check it. Which station serves a given ZIP code, and how far away it is, varies across the metro — the table below gives it per ZIP code rather than this page averaging it.
| Station | NOAA ID | Last spring freeze | First fall freeze | Season |
|---|---|---|---|---|
| Angwin Pacific Union College, CA | USC00040212 | April 7 | December 5 | 245 days |
| Markley Cove, CA | USC00045360 | March 6 | November 30 | 266 days |
| Napa Co AP, CA | USW00093227 | March 5 | November 21 | 256 days |
| Napa State Hospital, CA | USC00046074 | February 12 | December 4 | 299 days |
| Saint Helena, CA | USC00047643 | February 3 | December 4 | 306 days |
| Sonoma, CA | USC00048351 | March 2 | November 27 | 270 days |
These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.
Every ZIP code in Napa, CA
Zones are published per ZIP code, not per metro area, so this is the exact answer rather than the metro area'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 |
|---|---|---|---|
| 94503 | 9b | Napa Co AP, CA | 5.9 km |
| 94508 | 9b | Angwin Pacific Union College, CA | 1.4 km |
| 94558 | 9b | Markley Cove, CA | 12.7 km |
| 94559 | 9b | Napa State Hospital, CA | 4.0 km |
| 94562 | 9b | Saint Helena, CA | 10.1 km |
| 94567 | 9a | Angwin Pacific Union College, CA | 10.8 km |
| 94573 | 9b | Saint Helena, CA | 6.5 km |
| 94574 | 9b | Angwin Pacific Union College, CA | 3.9 km |
| 94576 | 9b | Angwin Pacific Union College, CA | 4.0 km |
| 94599 | 9b | Sonoma, CA | 13.2 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.
Your own ZIP
Work out your own dates
Each of these takes a ZIP code and answers for that ZIP alone, citing the station it used and how far away it is. There is a ZIP box in the header of every page.
-
What survives my winter?
Runs on the hardiness zone, so it answers for all of Napa, CA at once — zone across 74 perennial fruits, berries, vegetables and herbs.
- When do I start my seeds?
Dates every spring job from your own last freeze — sow indoors, set out, direct sow.
- When do I sow the next round?
How often each crop is worth re-sowing, and when the next sowing is due.
- What can I still plant?
Counts the growing days left before your first fall freeze, crop by crop.
Other places to compare
These metros span exactly the same zones — 9a–9b — so the same plants are in and out of range across them. The freeze dates and the spring calendar are their own.
- Wildwood-The Villages, FL — zones 9a–9b
- Hanford-Corcoran, CA — zones 9a–9b
- Baton Rouge, LA — zones 9a–9b
- Jacksonville, FL — zones 9a–9b
- Gainesville, FL — zones 9a–9b
- Lafayette, LA — zones 9a–9b
- Beaumont-Port Arthur, TX — zones 9a–9b
- Ocala, FL — zones 9a–9b
Gardening in California — zones 5b– 11a covers the whole state: how its 1,788 ZIP codes divide between 12 hardiness zones, and the freeze dates across every NOAA station in it.
Other metro areas in CA:
- Hanford-Corcoran, CA Zones 9a–9b
- Los Angeles-Long Beach-Anaheim, CA Zones 7b–11a
- San Francisco-Oakland-Fremont, CA Zones 9b–10b
- Riverside-San Bernardino-Ontario, CA Zones 7a–10b
- Sacramento-Roseville-Folsom, CA Zones 6b–9b
- San Diego-Chula Vista-Carlsbad, CA Zones 8a–11a
- Fresno, CA Zones 5b, 7b, 8a, 8b, 9a, 9b
- San Jose-Sunnyvale-Santa Clara, CA Zones 9a–10a
- Bakersfield-Delano, CA Zones 8a–9b
- Visalia, CA Zones 6b, 7b, 8b, 9a, 9b
- Santa Rosa-Petaluma, CA Zones 9a–10a
- Salinas, CA Zones 8b–10b
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.
- 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
The hardiness zone is the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. The freeze dates are NOAA's 1991–2020 Climate Normals, read from every station whose normals cover a ZIP code in this metro. Nothing here is estimated, and no station stands in for another.
This page names no single station on purpose. Picking one to represent a metro sounds reasonable and is not: the station serving the most ZIP codes is an artifact of where ZIP centroids happen to fall, and it selects a lock on the Monongahela for Pittsburgh and a far southern suburb for Chicago. A range across every station is true; a single cited date for a whole metro is not.