It's expected to be very hot and humid on Friday, and officials say you need to take precautions. The National Weather Service has issued a Heat Advisory from 11am until 9:00 PM for Frederick, Carroll, Montgomery and Howard Counties in Maryland. Temperatures are expected to reach 100 degrees, with the heat index at 105.

The Maryland Department of Health and Mental Hygiene has already activated its State Emergency Heat Plan for Central Maryland and the rest of the state. DHMH says the Plan encourages residents to take the necessary precautions to protect themselves against the heat. "Heat can kill so now is the time to take precautions," says DHMH Secretary Joshua Sharfstein.

Those actions include getting into a cool place, and drinking plenty of fluids. "If you know you're going to be outside for a long period of time, build that break in; build that cooling in," says Dr. Clifford Mitchell with DHMH. "And if you feel sick, and you feel even mild symptoms, get out of the heat. Get to some place cool; rehydrate."

Some of the mild symptoms of heat-related illness include feeling light-headed, sick to the stomach and dehydrated. If that's the case, you need to get out of the heat, find a cool place, and drink plenty of fluids.
When it comes to fluids, Dr. Mitchell says you should avoid alcohol. "One of the things alcohol actually does is dehydrate you more," he says. "So you never want to drink alcohol if you're feeling heat-related symptoms."

More serious symptoms include nausea, vomiting, cardiac problems and coma. Dr. Mitchell says if that happens, you need to call 911 and get medical attention.

Two of the extreme heat related illnesses include heatstroke and heat exhaustion. Heat stroke symptoms include dry red skin, convulsions, disorientation, delirium and coma. Treatment involves a rapid lowering of the body's temperature, using a cool bath or wet towels. Heat exhaustion may develop due to a combination of high temperatures and dehydration. Signs include extreme weakness, muscle cramps, nausea or headache. People may vomit or faint. The patient should be placed in a cool place, and drink plenty of fluids.

DHMH says so far this year, it has not recorded any heat-related deaths in Maryland. In 2011, there were 34 confirmed heat-related deaths in the state.