Another day of oppressive heat and humidity is expected today: heat advisory remains in effect until 10 p.m.

A heat advisory issued by the National Weather Service remains in effect until 10 o’clock tonight, with heat index values forecast to reach 104 degrees — possibly even higher — today.

The highest heat indices are expected in the early- to mid-afternoon, according to the weather service forecast. They could climb as high as 106 in northeastern Suffolk County, the weather service said in its early morning forecast update today. But a low-pressure system could bring somewhat cooler air — and some rain — into the area this afternoon and moderate hot temperatures and high heat indices, forecasters said.

The combination of the heat and humidity will increase the risk for heat-related health issues, especially for the elderly, people with chronic health problems such as lung and heart disease, people working outdoors, and other heat-sensitive groups of people.

Seniors and those with chronic health problems or mental health conditions are at an increased risk. Homes without air conditioning can be much hotter than outdoor temperatures.

Use air conditioning to stay cool at home or go to a place that has air conditioning. Check on vulnerable friends, family members and neighbors.

“Limit strenuous activities, stay out of the sun and drink plenty of fluids. Keep a close eye on the elderly and young children. Ensure your pets have shade and water,” Riverhead Supervisor Sean Walter said in a press release issued by the town police department.

If you must work outdoors today the Occupational Safety And Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments. Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency; call 911.

Take special precautions with your pets, Suffolk SPCA urges. “Your pet can become dehydrated quickly, so provide them with clean fresh water,” Suffolk SPCA Chief Roy Gross said. “Make sure they have a shady area to keep out of the sun. Appropriate shelter must be provided for dogs left outside,” he said.

“Know the warning signs. Symptoms can include difficulty breathing with excessive panting, weakness and possible seizures,” according to Gross. “Finally, if your pet exhibits any unusual symptoms, take him or her directly to a veterinarian.”

Remember, never — ever — leave your pet enclosed in a parked vehicle, even with the car windows partially open.

“The temperature inside a parked car can reach dangerous levels of 120 degrees in just a matter of minutes,” Gross said. “Your pet can quickly suffer brain damage or die from heatstroke when trapped in these high temperatures,” Gross said. Confining a companion animal in a vehicle in extreme temperatures is also a violation of state law, he said.

If you see a pet in a vehicle on a hot day, take immediate action. Note the car make, model, color and plate number, then go to the nearest stores and ask the managers to page the owner, Gross said. Call the police, who have the authority to enter the vehicle and rescue the pet.