Port Costa, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Port Costa, a community in Contra Costa County, California.
Today
92°F
Sunny
Sunny. High near 92, with temperatures falling to around 88 in the afternoon. Southwest wind 9 to 14 mph, with gusts as high as 20 mph.
7-day forecast for Port Costa
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 92°F | Sunny | 9 to 14 mph SW | 0% |
| Tonight | 57°F | Mostly Clear | 10 to 14 mph WSW | 0% |
| Wednesday | 86°F | Sunny | 13 mph WSW | 0% |
| Wednesday Night | 57°F | Mostly Clear | 9 to 13 mph SW | 0% |
| Thursday | 84°F | Sunny | 9 to 13 mph WSW | 0% |
| Thursday Night | 58°F | Mostly Clear | 9 to 13 mph WSW | 0% |
| Friday | 90°F | Sunny | 8 to 12 mph SW | 0% |
| Friday Night | 59°F | Mostly Clear | 12 mph SW | 0% |
| Saturday | 88°F | Sunny | 7 to 12 mph SW | 0% |
| Saturday Night | 60°F | Mostly Clear | 12 mph SW | 0% |
| Sunday | 84°F | Sunny | 9 to 14 mph SW | 0% |
| Sunday Night | 58°F | Mostly Clear | 15 mph SW | 0% |
| Monday | 78°F | Sunny | 15 mph SW | 0% |
| Monday Night | 57°F | Mostly Clear | 12 to 16 mph SW | 0% |
Forecast source: National Weather Service (api.weather.gov) for Port Costa (38.045, -122.185). Updated through the day.
Growing snapshot for Port Costa
Last spring frost
Jan 17
First fall frost
Dec 27
Growing season
346 days
Hardiness zone
9b
More local growing data for Port Costa: nearby ZIP 94569 weather · frost dates · planting calendar · California frost dates
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Climate data from the nearest NOAA station, Vallejo, Ca (3.9 mi from Port Costa). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.