R.Q.
If you are not new to exercising, you don't really need to restrict the time you exercise, unless the heat is bothering you. While exercising take note of how you feel, make sure you are well hydrated and periodically check your elevated heart rate (when you swap from jogging to walking is a good time to do this). Body temperatures over 100 degrees are cause for concern, but in my experience, unless you are doing an all out exercise session, it's not that common to get your body temp up that high. Take your temp before and after exercising to see where you're at. If your temp isn't rising a lot, don't worry too much, if it tends to jump up, take frequent breaks or opt for a day of swift walking instead of jogging. Also, feel your belly ;) if it's cool, don't worry your sweat is doing it's job :D if it's warm, that's good, but if it feels hot/feverish start your cool-down and finish up for the day.