When packing a school lunch during the extreme heat, parents need to be concerned not just with nutrition but with food safety as well, said a Baylor College of Medicine expert.

"A lot of the foods that parents typically pack in their children's lunch boxes, such as healthy turkey meat, cheese and yogurt, should perhaps be replaced with other options during extreme heat conditions," said Roberta Anding, a registered dietitian at BCM.

Golden hour of food safety

These foods follow the "golden hour" rule, meaning that they can only stay in an environment above 90 degrees for one hour before they need to thrown out, Anding said.

Some safe foods in the extreme heat include peanut butter and jelly sandwiches, fresh fruit and veggies – minus the ranch dip – and non-refrigerated milk that is packaged in a juice-box type container. Anding also recommended tuna or chicken "kits." These come with mayonnaise in a small packet that must remain unopened until it is mixed in at the lunch table.

Keep lunches safe

Anding has some other advice that will keep school lunches safe:

Don't assume a cold pack is staying frozen until your child eats lunch. Ask your child if it is still frozen when he or she finally sits down for lunch or if it is soft and mushy. If it's no longer frozen, avoid packing foods that must follow the golden hour rule.

Freeze juice pouches and other drink containers overnight. They can serve as an extra cold pack and should thaw by lunchtime.

Make sure to buy insulated lunch boxes to provide extra protection from the heat.

Pay attention to where you buy items in the grocery store. For example, if you buy pudding from the cereal aisle, it is safe to eat. But if the pudding was purchased in the dairy section, it must follow the golden hour rule.

Wash lunch boxes with warm soapy water nightly.

By following these basic food safety recommendations, parents can make sure their kids won't get sick while still getting the nutrition they need at lunch.