If you wait until you’re thirsty, it’s too late.

Thirst is just one symptom of dehydration, but you shouldn’t wait until you’re parched to drink water, according to Alison Harris, a nurse for on-demand health care provider DispatchHealth.

Although staying adequately hydrated is something to be mindful of all year long, it should be especially top of mind in the summer, Harris said.

WHAT YOU NEED TO KNOW

>> There’s more to dehydration than you might think.

In addition to increased thirst, dehydration has other common symptoms including dark urine, dry skin, headaches and muscle cramps, Harris said.

Other times, however, the symptoms could be confused for something other than dehydration, according to Harris.

“Sometimes it’s a very vague symptom,” she said. These ambiguous symptoms include feeling sleepy, tired, irritable or confused.

In severe but rare cases, symptoms of dehydration can include convulsions and even delirium, according to Harris.

>> It can take time for dehydration to settle in.

After spending time outside on a hot day, it might seem obvious to get a drink, but it might take longer for dehydration to settle in.

In some cases, dehydration can happen hours or even days later, Harris said.

“Your body is great at compensating until it can’t,” Harris said. This is why experts recommend hydrating days before strenuous activity, such as a marathon, and not waiting until the day of.

>> It doesn’t need to be hot outside for someone to become dehydrated.

The summer heat plays a role in dehydration, but it doesn’t take triple-digit temperatures to reach a breaking point.

Other weather conditions — such as humidity levels and dew points — also play a role in how much someone sweats.

When it’s muggy outside and humidity and dew points are high, someone might sweat more even if temperatures are relatively mild.

Once dew points reach 60 degrees, conditions will feel slightly muggy. When dew points reach 70 to 75 degrees, the air feels thick and oppressive, according to the National Weather Service.

“Make sure you’re listening to your body,” Harris said. “Make sure you’re not afraid to get help.”

>> There’s no magic number on the amount of water to drink.

When it comes to how much water someone should drink per day, experts often cite the “8X8” rule: eight 8-ounce glasses per day. That’s a good general rule to follow, Harris said, but everybody is different, so some people might need more and others less.

Other experts recommend measuring daily water intake based on weight. That’s another solid rule, but Harris said it doesn’t account for other factors, such as how many minutes someone exercises per day, what climate that person lives in and how much caffeine or alcohol that person consumes in a day.

Caffeine and alcohol are diuretics, which cause people to lose fluids, Harris said.

>> It takes more than just water to stay hydrated.

Water is great for staying hydrated, but that’s not all the body needs, Harris said. To stay optimally hydrated, the body needs a mix of water and electrolytes.

If they’re not doing so already, anyone who exercises regularly in the heat or spends several hours outdoors should consider drinking sports drinks to replace electrolytes lost through sweat, Harris said.