"Generally, food should be kept out of the refrigerator for no longer than two hours," says Sharon Franke, Kitchen Appliances Director, Good Housekeeping Institute. "But when it's really hot outside and you're in the sun, the rule of thumb is only one hour."

To find out which of the new coolers really perform and could give you this protection, the Good Housekeeping Institute filled the coolers with soda to the maximum capacity, topped them off with ice and put them in a chamber with a temperature of 90 degrees and a humidity of 50 degrees. Testers inserted thermocouples into the soda and measured the temperature inside the soda to see if it stayed cold and for how long.

Three coolers did a great job of keeping temperatures below 40 degrees for eight hours. "The Coleman Cooler Radio was a great cooler for an all day picnic. It holds the equivalent of 46 cans of soda, and the thing we really love about it is it has a built in AM/FM radio with an alarm clock and a weather band," says Franke.

For parties, Good Housekeeping recommends the Thermos Cold 'N Fold. It holds 108 12-ounce cans. And after the party, it collapses quickly to just three inches. Another recommendation is a soft-sided cooler from Thermos.

"The Thermos Geo Treck is a soft-sided cooler, but even though it's soft-sided, it stands up nicely so it's easy to fill. It keeps food cool for a whole day, and it has a nice shoulder strap so it is easy to carry," says Franke.

And Good Housekeeping has one more tip for a safe picnic: put ice blocks in your cooler instead of cubes. They keep longer. For more picnic tips, check out the July issue of Good Housekeeping or visit www.goodhousekeeping.com.