The sweltering heat is not letting up as temperatures climbed into the  90's Wednesday and heat indices topped the 100's. And that has health officials concerned about heat-related illnesses.

They're particularly worried about the elderly and the very young in the community.

So far, about six people have been seen at Mayo in La Crosse for heat-related illnesses, ranging from fatigue to mild heat exhaustion.

Gundersen has seen a small increase of patients with most being heat exhaustion.

Doctors say it's vital to stay hydrated because once heat exhaustion sets in, it's hard to overcome. "You need to stay on top of being hydrated because once you've become dehydrated it's hard to catch up and your body, especially if you're outside working, still continues to require the same, if not more, fluids, so once you feel the symptoms sometimes it's almost too late already," said Mayo Clinic Health System Emergency Medicine Physician Eric Grube.

Other recommendations include staying in shaded areas and wearing loose fitting clothing.