The city where I live has to have one of the worst general environments for outdoor exercise. The heat index typically makes felt temperatures hit triple digits or quite close to them, and the high humidity makes it feel like you step into a sauna with each venture outside. It's like this mostly throughout mid to late Spring all the way into mid Fall. Winter temperatures can still be in the 80s (degrees Fahrenheit), but the humidity decreases significantly. So, typically the best time for an outdoor run or something of that nature throughout the seasons is in the wee hours of the morning or after sundown.
All this being said, I prefer to exercise on my treadmill and elliptical where I have my precious AC. I'm not looking for a bikini-body so much as I am trying to develop a habit of consistency. I typically exercise 45 minutes on either one, followed by a brief cool-down (10 minutes), and rounding it all off with stretching to maintain flexibility. I try to do this every day.
There's a great book called "Dance Anatomy" that's part of a series of books on physical activities and what parts of your body they involve. It gives quick exercises on how to isolate and work out different areas of the body. It also gives tips on training and what exercises to do often, which to do every once in a while, how to warm up etc. It made me really aware of my body and how I use it in dance. It also is great in helping prevent injury.