Infants and children up to age four are most at risk for heat-related illnesses. The best way to prevent the effects is to encourage your kids to drink fluids even before they’re thirsty. Water is best, especially if the alternative is a sugary juice or lemonade—those will cause kids to lose even more body fluid. Dress your children in light, loose-fitting clothing and wide-brimmed hats, and if possible, keep them indoors part of the day, especially if air conditioning is available. That will help keep their bodies cool when they go back outside into the heat.