NORFOLK -- Experts say children are even more susceptible to heat dangers than adults.
Tim Killeen says his kids' personalities change after playing for an hour in the heat.
"He gets a little frustrated and tired," said Killeen.
Dr. Tina Dolenti, with the sports medicine department of Children's Hospital of the King's Daughters, says there's a reason for this.
"Children's temperature systems aren't developed well enough yet, so they can't sweat as easily and can't regulate their temperature as well as an adult can. They tend to overheat more quickly," Dolenti described.
The latest study out of Loyola University Chicago says children must hydrate with water after 20 minutes of vigorous play in the heat. Sports drinks are only required if a child engages in vigorous exercise for more than 60 minutes.
13News noticed the kids at a picnic on Thursday enjoyed juice more than water.
Dr. Polenti says juice can be fine, but there's a better compromise.
"Typically I say water down the juice."