Today's heat index will reach as high as 110f this afternoon. Although our actual high temp is only in the mid 90's, the dew point is so high that it will make things feel 10-15 degrees hotter than it really is. It's difficult for your body to cool itself in these conditions and can quickly lead to dehydration and heat stress.
Drink water before, during and after activity. Take breaks in the air conditioning. Public libraries and malls are great 'free' places to stay cool. Check on small children and the elderly as they are most at risk for heat stress.
Saturdays heat index may reach as high as 112f as the humidity rises further. At least we have a 20% rain chance today, Saturday and a 30% rain chance on Sunday.