Climate averages 1991–2020
Union City weather
in August.
A hot, very dry month: the warmest and the 2nd driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
August is a hot month in Union City: daytime highs average 28.0°C and nights cool to about 15.1°C. By daytime temperature it is the warmest month of the year.
Expect about 1.0 mm of rain on fewer than one day, which makes August a very dry month (the 2nd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 37 min on an average August day.
The nearest other city in this atlas is Fremont (6 km away). In August its highs average 27.6°C, about as warm as Union City, with 1.0 mm of rain.
Among the 498 cities listed in the United States, Union City ranks joint 325th of 498 for the warmest August highs and joint 51st of 498 for the driest August (rainfall, lowest first). The mean August high of those 498 cities is 29.9°C; Union City is 1.9°C cooler than that mean.
From August to September, average highs fall by 0.5°C to 27.4°C, and monthly rainfall rises from 1.0 mm to 1.9 mm.
The annual picture
August in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Union City climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 14.3°C5.9°C | 5.9°C | 91 | 8.9 | 9.910 h |
| February | 15.5°C6.9°C | 6.9°C | 96 | 9.1 | 10.811 h |
| March | 17.2°C8.2°C | 8.2°C | 75 | 9.1 | 11.912 h |
| April | 19.1°C9.2°C | 9.2°C | 40 | 5.7 | 13.113 h |
| May | 22.1°C11.1°C | 11.1°C | 19 | 3.4 | 14.214 h |
| June | 25.6°C13.0°C | 13.0°C | 4.0 | 0.9 | 14.715 h |
| July | 27.9°C14.8°C | 14.8°C | 0.9 | 0.2 | 14.514 h |
| August, selected | 28.0°C15.1°C | 15.1°C | 1.0 | 0.2 | 13.614 h |
| September | 27.4°C15.1°C | 15.1°C | 1.9 | 0.4 | 12.512 h |
| October | 23.7°C13.1°C | 13.1°C | 23 | 2.9 | 11.311 h |
| November | 17.8°C9.3°C | 9.3°C | 43 | 5.7 | 10.210 h |
| December | 14.0°C6.3°C | 6.3°C | 83 | 8.9 | 9.610 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
August in nearby cities
- Fremont in AugustUnited States · 6 kmHigh 27.6°C · Low 15.2°C · 1.0 mm rain
- Hayward in AugustUnited States · 10 kmHigh 26.7°C · Low 14.5°C · 1.4 mm rain
- Pleasanton in AugustUnited States · 15 kmHigh 28.9°C · Low 14.8°C · 2.1 mm rain
- San Ramon in AugustUnited States · 21 kmHigh 28.1°C · Low 14.7°C · 1.4 mm rain
- Milpitas in AugustUnited States · 21 kmHigh 28.7°C · Low 15.7°C · 1.0 mm rain
- Redwood City in AugustUnited States · 23 kmHigh 24.5°C · Low 14.4°C · 0.7 mm rain
- Mountain View in AugustUnited States · 24 kmHigh 26.3°C · Low 14.8°C · 1.0 mm rain
- Livermore in AugustUnited States · 24 kmHigh 29.5°C · Low 14.8°C · 2.1 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Union City) is explained once on the Union City year overview and on the Sources, method and limits page.
Fremont, Mountain View and Milpitas lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.