Whereas Europe has been experiencing searing temperatures recently, it is becoming clear every passing day that heat waves have become more frequent globally and last longer. If the body is exposed to extreme temperatures climbing to more than 30 degrees Celsius (104 degrees Fahrenheit), there's a risk of overheating.

During hot days, it's important to make sure that you and those around you don't become overheated – especially if you're working or exercising outdoors. Although our body has ways to cool itself down, sometimes it absorbs more heat than it can give off.

"When temperatures are high, we sweat more, since (the evaporation of) sweat cools the body externally," said Dr. Jorg Schlaak, chief physician in the Department of Internal Medicine at Ameos St. Clemens Hospital in Oberhausen, Germany. "On extremely hot days, this causes a fluid loss of up to 2 liters more than usual."

Profuse sweating also depletes the body's salt levels. So if you don't replenish the lost fluids and salts, and/or are exposed to bright sunlight for too long, you're risking a heat emergency. Here's how to spot the symptoms and take countermeasures.

Heatstroke

This occurs when the body is unable to dissipate the heat buildup quickly enough by sweating. In just 10 to 15 minutes, the body temperature can rise to more than 40 degrees Celsius, warns Germany's Federal Center for Health Education (BZgA).

Symptoms of heatstroke are hot, dry skin along with a rapid heart rate, cramps and vomiting. Loss of consciousness can also occur. Heatstroke is a medical emergency, so don't hesitate to call the local emergency number – even if a heatstroke victim who has fainted regains consciousness quickly.

"Medical care is absolutely essential," emphasized Schlaak, who says the primary treatment is the administration of intravenous fluids to restore the body's fluid and salt balance.

Before the paramedics arrive, get the person to a shady place. Their upper body should be elevated.

The German Red Cross (DRK) advises cooling their body too, for example with wet cloths. However, don't put ice on the skin. If they're conscious, you can offer them something to drink: water, juice mixed with sparkling mineral water or herbal tea.

Sunstroke

Going bareheaded in intense sunlight for too long can irritate the meninges, thin layers of tissue that envelop and protect the brain. This condition is sunstroke, the BZgA says. In severe cases, brain swelling may occur.

Symptoms include headache and dizziness along with a hot and highly flushed head. Nausea and vomiting are also common. The symptoms can also occur long after you've gotten out of direct sunlight.

"Young children are especially at risk and should never go without a cap in the blazing sun," Schlaak said, adding that they've got less hair on their head than adults do and also a thinner skull, and are therefore more sensitive to sunlight.

Someone with sunstroke should get into the shade as quickly as possible. It's best to keep their head and upper body slightly elevated, according to the BZgA, and they should drink lots of fluids. If they lose consciousness, the DRK advises calling the local emergency number.

Heat exhaustion

Extreme thirst and feeling weak and lethargic could be signs of heat exhaustion. Further symptoms include cool, moist skin and rapid, shallow breathing, according to the BZgA.

Like other heat emergencies, heat exhaustion should be taken seriously, as it can develop into heatstroke. To prevent this from happening, Schlaak says it's imperative to react quickly if you're feeling dazed and weak.

As is the case with heatstroke, someone with heat exhaustion should quickly get to a cooler place and drink plenty of fluids. If their condition doesn't improve in an hour, or their body temperature rises to more than 38 degrees Celsius, the BZgA says they should see a doctor.