It is good to get advice that takes a general idea such as the article that I am linking to about heat and then breaks it down for better understanding. Yes working out in the heat can be very good for the muscles but only up to a point. Essentially, humidity can be the cause of a heat issue. Exercising when it is 90 and less than 30% humidity is better than 80 and over 60% humidity. In all cases, especailly those of high humidity, hydration is very important. So enjoy the heat but watch the water/humidity!
http://www.reuters.com/article/2012/06/18/uk-fitness-heat-idUSLNE85H01520120618
