Taking the local weather in San Antonio into account is an important factor for planning your visit, especially if you plan to spend your trip by the pool. The hottest months are usually January and December, with an average temperature of 28°C, while the coldest months are July and June, with an average of 18°C. The rainiest months in San Antonio are October, November, December and April, with each month seeing an average of 190 mm of rainfall.