Climate Insights for Castro Valley

The climate in Castro Valley is temperate. The average annual temperature is 15°C and approximately 465mm of precipitation falls per year. Gennaio is the wettest month, receiving around 102mm of rainfall. Castro Valley is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: Settembre, Agosto, Luglio. The coldest months are Dicembre, Febbraio, Gennaio, when temperatures can drop to 7°C.

Castro Valley sees moderate temperature variation throughout the year, ranging from 7°C to 26°C. The warmest month is Settembre, when average highs reach 26°C and the mean temperature sits around 19°C. Dicembre is the coolest month, with minimum temperatures around 7°C and an average of 10°C. On average, daily temperatures fluctuate by about 10°C between overnight lows and afternoon highs. The sharpest temperature change occurs between October and November, with a 4°C shift in average temperatures.

Castro Valley is a relatively dry area, receiving approximately 465mm of precipitation annually, which averages out to around 39mm per month. The wettest month is January, averaging 102mm of rainfall. December and March also tend to see above-average precipitation. The driest month is August, with just 0mm. That's 102mm less than January, the wettest month. Rainfall is heavily concentrated in certain months, creating a distinct wet and dry season. Visitors should plan around these patterns, as the difference between peak and low months is dramatic.

Castro Valley is mildly breezy, with an average annual wind speed of 17km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is May, averaging 19km/h, though still comfortable for most outdoor activities. The calmest conditions occur in November, with average winds dropping to 13km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 6km/h gap between the calmest and windiest months. Wind tends to pick up during the summer months. The seasonal averages are 15km/h in winter, 19km/h in spring, 18km/h in summer, 15km/h in autumn.

It is currently spring in Castro Valley, which began on March 20, 2026. Castro Valley is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in Settembre at around 26°C, while the coldest stretch bottoms out in Dicembre near 7°C. Summer is next, beginning on June 21, 2026 — 92 days from now.

The best time to visit Castro Valley is during Maggio, Giugno, Luglio, Agosto, Settembre and Ottobre, when the weather is most comfortable for travellers. During these months, average temperatures hover around 17°C with modest rainfall averaging 7mm per month. By contrast, Dicembre can be quite cold with temperatures dropping to 7°C. With minimal rainfall expected, you can pack light and plan outdoor activities with confidence.

The table below shows monthly climate averages for Castro Valley based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.