TULSA, Oklahoma - The extreme heat is only going to get worse before it gets better.

EMSA said they have already treated and transported six people with symptoms of heat-related illness, just since midnight Tuesday. Their ages ranged from a 58 years old to 30 years old.

And temperatures are forecasted even higher for Thursday.

EMSA treated and transported about 400 people last year for heat illnesses and say they could be heading that way again, especially with even more people now at risk.

EMSA spokesman Chris Stevens said, "If you do have a heat related illness, experienced that in the past—last year, last week—it doesn't matter, your body is now forever and will be more susceptible to heat related illness. It's going to affect your organ system."

Some good rules to remember for the heat are to pre-hydrate, wear loose, light colored clothing and a wide brimmed hat, and check on friends face-to-face so that you can actually see their conditions.

EMSA said most of the patients they have treated for heat related illness were working outdoors, either for work or at home. But they say heat can sicken anyone.

They recommend you drink plenty of something non-caffeinated and non-alcoholic before spending any time in excessive heat.

EMSA said that once they respond to five or more heat-related calls in a 24-hour period, then they issue a Heat Alert. This is the third day in a row EMSA has issued a Heat Alert.

We have more information about dealing with extreme heat here, in our Weather 101 section.