Castro Valley and Union City have remarkably similar climates.
The year at a glance
Averages from 30 years of climate history, 1991-2020
| Castro Valley | Metric | Union City |
|---|---|---|
| 257 days | Sunny daysclear or partly cloudy skies | 251 days |
| 18 in | Precipitationper year | 19 in |
| 53 days | Wet daysrain or snow per year | 55 days |
| 0 in | Snowfallper year | 0 in |
| 8 days | Hot daysabove 90 °F | 11 days |
| 1 days | Freezing nightsat or below 32 °F | 2 days |
| 73% | Humidityaverage relative | 72% |
| 59 °F | Average temperatureyear round | 60 °F |
Monthly temperatures
Average daily high and low for each month, in °F. The gap between the two lines is what an ordinary day feels like across the year.
Daily highs
Daily lows
View monthly temperatures as a table
| City | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Castro Valley high | 59 | 62 | 64 | 67 | 69 | 74 | 74 | 76 | 77 | 73 | 65 | 59 |
| Union City high | 59 | 62 | 65 | 67 | 71 | 75 | 77 | 78 | 78 | 73 | 65 | 59 |
| Castro Valley low | 43 | 45 | 47 | 49 | 52 | 55 | 57 | 58 | 57 | 53 | 47 | 43 |
| Union City low | 43 | 45 | 47 | 49 | 52 | 55 | 57 | 58 | 57 | 53 | 47 | 43 |
Monthly precipitation
Total rain plus melted snow for each month, in inches. Taller bars mean wetter months.
View monthly precipitation as a table
| City | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Castro Valley | 3.5 | 3.7 | 2.8 | 1.3 | 0.7 | 0.1 | 0.0 | 0.1 | 0.1 | 0.8 | 1.6 | 3.2 |
| Union City | 3.6 | 3.8 | 2.9 | 1.6 | 0.8 | 0.2 | 0.0 | 0.0 | 0.1 | 0.9 | 1.7 | 3.3 |
Monthly sunny days
Days each month with clear or partly cloudy skies, so compare the same month between cities.
View monthly sunny days as a table
| City | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Castro Valley | 14 | 13 | 16 | 20 | 23 | 26 | 29 | 29 | 28 | 25 | 18 | 16 |
| Union City | 14 | 13 | 15 | 18 | 22 | 25 | 29 | 29 | 28 | 24 | 18 | 15 |
Keep comparing
Nearby cities and popular picks for each side of this matchup. Any two cities can be compared from the home page.
Castro Valley vs another city
- Castro Valley vs Fairview, CA
- Castro Valley vs Cherryland, CA
- Castro Valley vs Ashland, CA
- Castro Valley vs San Lorenzo, CA
- Castro Valley vs San Leandro, CA
- Castro Valley vs Hayward, CA
- Castro Valley vs New York, NY
- Castro Valley vs Los Angeles, CA
- Castro Valley vs Chicago, IL
- Castro Valley vs Houston, TX
- Castro Valley vs Phoenix, AZ
- Castro Valley vs Philadelphia, PA
Union City vs another city
- Union City vs Hayward, CA
- Union City vs Fairview, CA
- Union City vs Newark, CA
- Union City vs Cherryland, CA
- Union City vs San Lorenzo, CA
- Union City vs New York, NY
- Union City vs Los Angeles, CA
- Union City vs Chicago, IL
- Union City vs Houston, TX
- Union City vs Phoenix, AZ
- Union City vs Philadelphia, PA
About this data
Every figure on this page is a 30 year average computed from daily climate history for 1991-2020, using each city's own coordinates. Wet days count days with measurable precipitation, calibrated against the wet day counts in NOAA's published climate normals. Sunny days count clear plus partly cloudy days, defined as average cloud cover of 63 percent or less and calibrated against NOAA's published sky cover tables. Snowfall figures are model estimates anchored to NOAA station measurements near each city.
Weather data by Open-Meteo.com (CC BY 4.0). Contains modified Copernicus Climate Change Service information (ERA5, ERA5-Land).