Bob, 69, was recently on the golf course when he suddenly felt weak and dropped to his knees as waves of dizziness swept over him. An ambulance was called.

At the hospital, we discovered Bob had become seriously dehydrated. That triggered an attack of atrial fibrillation, a serious heartbeat irregularity that ups stroke risk and can cause heart failure and other complications as well.

The whole body — including heart tissue — is filled with water. If you’re out in the heat and sweating, your body loses water, which can lead to dehydration.

When that happens, the body’s electrolytes (minerals in your blood) such as potassium become depleted.

Potassium aids nerve conduction and muscle contraction, both of which play key roles in keeping the heart beating at a normal rhythm.

That’s why depleted potassium levels can trigger atrial fibrillation — which, though not usually life-threatening, can lead to serious complications.

In addition to the heat, playing golf and the alcohol he’d consumed at lunch (a martini) contributed to Bob’s risk of dehydration and heat-induced atrial fibrillation.

Here are some tips to avoid dehydration during the summer months:

• Don’t go out in the sun during the hottest hours, which are between 10 a.m. and 2 p.m.

• Don’t wait until you’re thirsty. Drink water all day, especially before you head outside.

• Sports drinks with electrolytes are also good. They can help if you feel symptoms of dehydration as well.

• Avoid alcohol. Cocktails are tempting, but alcohol is dehydrating.

• Don’t drink caffeinated beverages, including coffee, tea with caffeine, many sodas, and most energy drinks.

• Snack on fruits and veggies. They are high in water content.

• If you like spicy foods, go ahead. Although they taste “hot,” they actually cool the body down.

• If you’re out walking or being active, stay close to restaurants, convenience stores, or other places that offer cooler temperatures and beverages if you need them in an emergency.

• If you’re at the beach or pool, a dip in the water will cool your body off.