Planning for the weather is an important factor for making your trip to Semarang a success, especially when you’re splurging. The hottest months are usually September and October, with an average temperature of 28°C, while the coldest months are July and August, with an average of 27°C. The rainiest months in Semarang are January, December, February and March, with each month seeing an average of 351 mm of rainfall.