NEW YORK (CBSNewYork) — Many of us are firing up the grill this holiday week, but health experts warn the summer outdoor cooking season is also the time they see more cases of food poisoning.

“Because of hot, humid temperatures and because folks are often away from the kitchen at picnics and cookouts, food-born illnesses may actually increase,” Chris Bernstein, spokesman for the U.S. Department of Agriculture, tells CBS News’ Don Champion.

Harmful bacteria can actually multiply more quickly when it’s hot outside.

The USDA says to stay safe, clean your hands before preparing food, keep raw food separated from cooked, and cook everything to a safe internal temperature and chill food promptly and properly.

Whether you’re grilling in the backyard or barbecuing in a professional smoker, experts say a food thermometer is the best way to make sure everything is cooked thoroughly.

Yet only a third of Americans use one.

George Moore is a pitt master at a smokehouse near Dallas, and showed CBS News’ Champion how to get a good read.

“You want to stick it in the fattest part of the meat which is going to be where you can get the most accurate reading of your internal temp,” Moore said.

Bernstein says it takes more than just looking at your meat to see if it’s reached a safe internal temperature.

“That magic number is really the only way to be sure that you’ve killed any bacteria that might be present,” he said.

The USDA also reminds us that anything perishable should usually not sit out at room temperature for more than two hours. In temperatures over 90 degrees, nothing should be left out for more than an hour.

Also, don’t rely on the sniff test to check if something is still good — foodborne illnesses like salmonella and e-coli are caused by bacteria that doesn’t have any smell to it.