Last week was pleasant here in Muscat, the capital city of Oman. The temperature was in the high 80s to low 90s, and the heat index was barely above 100. Maybe 105, but not much more than that. In July, that’s heaven in Muscat.

When I talk about the heat in Muscat, people say it’s a dry heat, though, right? Well, no. Muscat is a port city. It has ocean all along one side and mountains that trap the humidity from all that water on the other. It’s an urban pressure cooker. A giant oriental steam basket.

Therein lies the problem. The humidity of the air makes the heat especially dangerous. With dew points easily in the 70s — and even into the 80s at night — Muscat is a dangerous place to be hot. At 7 a.m. today in Muscat, the temperature was 99 degrees Fahrenheit. The heat index was already 107 degrees. Within moments of stepping outside, one starts to sweat.

As we all learned back in elementary school, the reason we sweat is to cool off. It didn’t make much sense back then, and it didn’t really seem to our unformed minds like it worked. But, of course, it does. Evaporation is an endothermic process in which heat is absorbed as the water turns into gas. The air absorbs the heat and our skin is cooled.

This is great in the interior regions of Oman like Nizwa, the one-time capital, or Buraimi, a once-disputed area on the northwest border with the United Arab Republic. In coastal cities such as Sohar, Muscat and Sur, however, the humidity is often so high the sweat does not evaporate. No cooling takes place. The moisture just drips off, or soaks your clothes. There is no exothermic reaction. Your body just gets hotter and hotter, and the sweat rapidly dehydrates you.

Thus, the admonition to visitors who are not used to such heat and humidity to drink water constantly. It’s not an issue of rehydration, it’s an issue of constant hydration. If you begin to feel dehydrated here, it’s too late. You have to find a cool place, rest and drink.

A good test is actually urine. If one’s urine is dark, drink. Drink a lot of water. If it’s light, everything’s OK.

One must constantly have a bottle of water, everywhere. It doesn’t have to be ice-cold water. It can be chilled or room temperature (remembering that an un-air conditioned room is 100 degrees or more).

Coffee and soda don’t figure into the equation, especially colas. While they are not taboo, they actually aid dehydration, so even more water is required until the caffeine is out of the system. But, in fact, even water may not be enough in this extreme heat. It only replaces fluids, not electrolytes.

“Electrolytes regulate our nerve and muscle function, our body’s hydration, blood pH, blood pressure, and the rebuilding of damaged tissue,” according to medicalnewstoday.com. “Our muscles and neurons are sometimes referred to as the ‘electric tissues’ of the body. They are reliant on electrolyte movement between extracellular, interstitial and intracellular fluid (fluid inside, outside or between cells).” These electrolytes include potassium, bicarbonate, sodium (or salt) and calcium. The loss of electrolytes can cause muscle cramping, tics or twitches, and in extremity seizures.

That’s what Gatorade and PowerAde were designed for. Those drinks, however, are virtually unknown here.

Here in Oman, they drink a product called, somewhat unappealingly, Pocari Sweat. It is not, in fact, refined from anyone’s sweat. Admittedly it does take some getting over to actually pop the top and drink up. It contains sugar, but not in the quantity or cloying sweetness of the American drinks.

Pocari Sweat, and yes, it’s just as fun to say out loud as it looks, was developed by Otsuka Pharmaceutical Co. of Japan. It’s manufactured in India and imported in huge quantities to Oman. A can or two a day is good for moderate outdoor activity.

Just walking from the air conditioned car to an air conditioned building and back probably doesn’t require anything more than water. But if the shirt is damp, the sweat is running down one’s legs, and the socks are like wet sponges, Pocari Sweat should be part of the day’s routine to supplement the water.

By the way, Omanis are very good at air-conditioning. Most modern houses have an individual unit in each room rather than central air conditioning. Older homes have window units, but the modern ones are mounted toward the ceiling in each room. They are usually turned off until the room is used, which saves a lot of energy. Every single village in Oman has electricity, something the sultan has accomplished in the 46 years he’s been in power. So even in the smallest towns in the most remote areas air conditioners are often in use.

One more note on the effects of evaporation. In olden days, and even today in the villages, Omanis used evaporation to chill water. Large unglazed clay vessels, holding about a quart, are filled with water and suspended from a window with rope or twine. These vessels are porous, and water soaks through. The surface water evaporates, cooling down the vessel and the water inside. Although it isn’t cold, it’s cooler than the surrounding air, and thus quenching.

Evaporation! It’s cool!