Port Costa, CA Weather & Growing Conditions
This Afternoon
80°F
Sunny
Sunny, with a high near 80. West southwest wind around 12 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 80°F | Sunny | 12 mph WSW | 0% |
| Tonight | 56°F | Mostly Clear | 12 mph SW | 0% |
| Saturday | 82°F | Sunny | 7 to 10 mph SW | 0% |
| Saturday Night | 57°F | Partly Cloudy | 12 mph SW | 0% |
| Sunday | 74°F | Partly Sunny | 12 mph SW | 1% |
| Sunday Night | 56°F | Mostly Cloudy | 13 mph SW | 1% |
| Monday | 75°F | Mostly Sunny | 13 mph SW | 0% |
| Monday Night | 56°F | Partly Cloudy | 8 to 13 mph SW | 0% |
| Tuesday | 79°F | Sunny | 7 to 10 mph SW | 0% |
| Tuesday Night | 57°F | Mostly Clear | 3 to 10 mph SW | 0% |
| Wednesday | 91°F | Sunny | 2 to 6 mph W | 0% |
| Wednesday Night | 60°F | Mostly Clear | 2 to 6 mph WSW | 0% |
| Thursday | 90°F | Sunny | 2 to 9 mph WSW | 0% |
| Thursday Night | 60°F | Partly Cloudy | 6 to 9 mph SW | 0% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Port Costa, CA
Last spring frost
Jan 17
First fall frost
Dec 27
Growing season
346 days
Hardiness zone
9b
Explore more for Port Costa, CA: full frost dates · planting calendar · California frost dates
Climate data from the nearest NOAA station, Vallejo, Ca (3.9 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.