A trip through the sprinkler may cool your kids off in the heat, but there is no substitute for a cold drink to prevent dehydration. And it may take more than you think.

Dr. Darla Gallentine, of Pediatric Express Urgent Care in Morrisville, said a sip from the water fountain is not enough for active kids, especially when temperatures are high. But the key is to start hydrating early.

"One thing that parents don't often think of is making sure their kids drink plenty before they go outside," said Gallentine. "So tank them up before they go outside in the heat and then, every 20 minutes, a school-aged child needs about four to five ounces of fluid, either water or a sports drink, and then an older child needs probably eight to nine ounces every 20 minutes."

Parents should watch for signs of heat stress, which include: headache, fatigue and nausea. When that happens, kids should get in the shade and have something to drink to prevent further problems.

As for the mist sprayers and ice packs athletes use to cool down on the sidelines, Gallentine said they may provide relief, but it's critical to rehydrate from the inside out.