Castro Valley has mild winters with temperatures ranging from near-freezing to the mid-20s Celsius, while spring brings warmer days with highs often reaching the low to mid-30s. Summer months are hot, with temperatures frequently soaring above 40 degrees Celsius, although there's some variation between June and July. Autumn is generally cooler, with temperatures dropping back into the single digits to mid-teens by November. Winters are typically the coolest time of year, with temperature fluctuations from just below freezing to the low 20s. Overall, Castro Valley's climate is moderate, with warmest days often in May and June before the heat peaks in July and August.