Fourth of July weekend is bringing the heat. Here’s how to protect yourself.

Almost all of Maryland is under a heat advisory starting at 11 a.m. Wednesday amid a heat wave expected to cook most of the mid-Atlantic and Midwest.

High temperatures are expected to hit 100 degrees on Wednesday afternoon, though it could feel closer to 108 degrees outside because of the high humidity, according to the National Weather Service. There is a chance of rain showers and thunderstorms throughout the afternoon as well. It’ll remain hot even after the sun goes down, staying around 79 degrees.

Those conditions are expected to worsen throughout the week, especially on Thursday, when the heat index in the Baltimore area could hit 113 degrees. Wednesday’s heat advisory is expected to become an Extreme Heat Watch on Thursday and Friday.

The weather service said “significant heat risk will linger” on Saturday as people celebrate Independence Day around the state.

Gov. Wes Moore declared a State of Preparedness on Tuesday ahead of the hot holiday weekend, activating the Maryland Department of Emergency Management to prepare for the heat wave. Baltimore Mayor Brandon Scott also issued a Code Red Extreme Heat Alert for Wednesday through Saturday.

Dr. Louis Piper, an emergency department physician at Luminis Health Doctors Community Medical Center in Lanham, said he began seeing patients with heat-related illnesses in the emergency room Tuesday as temperatures rose.

“Particularly people who were out doing yard work and things like that, people who were exerting themselves in the hot sun, and not really paying attention to their fluid intake,” he said. “I anticipate the numbers are gonna go up even more when we start getting crowds of people coming into the DMV.”

How you can stay safe while celebrating

There are many heat-related illnesses, but heat exhaustion and heat stroke are two of the most common, and they can be fatal.

If you’re going to be outside this weekend, it’s important to stay hydrated. If you’re drinking alcohol, Piper said to drink water and electrolytes alongside alcoholic beverages at least as much as you usually would, if not more.

“You want to drink before you feel thirsty,” Piper said. “Because if you’re already starting to feel thirsty, that means you’re behind.”

People with chronic conditions, like diabetes or high blood pressure, are more susceptible to heat-related illnesses, he added, as are children and older adults. If you have a spray bottle or a hand-held fan, Piper recommends using those to stay cool. Wearing loose, lightweight, light-colored clothing can also help.

If you start to feel light-headed or dizzy, it’s best to find a place indoors with air conditioning to cool off. If symptoms escalate, you should see a doctor or call 911.

Symptoms can include:

• Muscle pain or spasms
• Feeling hot but not sweating
• Heart racing
• Vomiting
• Extreme weakness
• Nausea
• Disorientation
• Slurred speech
• Rapid, shallow breathing

How the city and state will operate during extreme heat

During extreme heat emergencies, the Maryland Department of Emergency Management and the Department of Health work together to conduct outreach to local authorities, deploy resources where needed, and help respond to any power or water outages, according to the state’s extreme heat emergency plan.

A State of Preparedness has been issued to get ahead of heat threats and avoid a State of Emergency.

In Baltimore, cooling centers activated on Wednesday will remain open through Saturday. All 22 city pools will remain open through the holiday weekend and will extend their hours:

Pools will be open July 1-2 from:

• 12-2 p.m.
• 2:30-4:30 p.m.
• 5-6:30 p.m.
• 7-8:30 p.m.

Pools will be open July 3-5 from:

• 11 a.m.-1 p.m.
• 1:30-3:30 p.m.
• 4-6 p.m.
• 6:30-8:30 p.m.

Baltimore City Recreation and Parks suspended all outdoor athletic programming but has moved some indoors, according to the mayor’s office.

The city also said the Department of Public Works would suspend recycling services so its workers could focus on trash pickup, but added that residents should expect additional changes to sanitation operations due to the weather.

A list of cooling centers in every Maryland county is available on the state Department of Health’s website.

Banner reporter Courtney Knight contributed to this story.