Lambton Public Health (LPH) is reminding residents to take certain measures to avoid heat-related illnesses as hot and humid conditions continue.
The health unit issued an extended heat warning on Monday as the stifling weather is expected to continue through Tuesday.
Environment Canada first issued a heat warning for Sarnia-Lambton on June 20.
Warning Preparedness Meteorologist Steven Flisfeder said a new record high was set on June 22, when the temperature climbed to 34.5 C.
During heat events, people's bodies may not be able to cool properly, which can lead to heat exhaustion or heat stroke.
LPH Acting Supervisor for Health Protection Theresa Warren said symptoms of heat exhaustion can include rapid breathing, dizziness or fainting, vomiting, rapid heart rate, extreme thirst, and decreased urination that is unusually dark in colour.
"If you're experiencing these symptoms, you're recommended to move into a shaded or air conditioned area, drink plenty of water, and rest," she said. "If the symptoms persist, you want to seek immediate medical attention."
Warren said heat strokes are considered a medical emergency, and anyone experiencing one should contact 911 immediately.
"If you're caring for anyone who has a high body temperature, or is dizzy, is fainting, or is confused, or has stopped sweating... then you should call 911 and bring them to the hospital," Warren said.
Those who are vulnerable during extreme heat events include older adults, young children, people with chronic illnesses, pregnant individuals, people who work outdoors, and people who are underhoused or experiencing homelessness.
LPH is advising residents to drink plenty of fluids -- especially water, to reschedule or plan outdoor activities during cooler parts of the day, to wear loose-fitting and light-coloured clothing, to check in on neighbours and loved ones, and to spend time in cool areas.
Cooling centres are located throughout Lambton County and are available to provide relief during extreme weather alerts. The locations include recreation centres, health centres, libraries, and other public and municipal buildings.
The hours of operation differ depending on the location. A full list of cooling centres can be found on the health unit's website.