Planning for the weather is a good way to make your trip to Kisarazu relaxing and enjoyable, especially when you’re splurging. The hottest months are usually August and July, with an average temperature of 25°C, while the coldest months are January and February, with an average of 9°C. The rainiest months in Kisarazu are October, September, June and July, with each month seeing an average of 220 mm of rainfall.