We have spent summer vacations in San Antonio. One year during the 4th of July. It is hot but it is a dry heat. It was 105 when we were at the Alamo and only felt like 80 by Missouri standards :) We love San Antonio. The Mission trail is very interesting, the Alamo is just amazing, the River Walk is nice and cool no matter how hot it is and Sea World is fantastic. If you can go to the El Mercado (street vendors and farmers market area) when they are having a street fair, you can get wonderful food and unique gift items for very reasonable prices. Just my two cents but San Antonio is fun!