Rivers are popular spots on hot days, but people standing around doing nothing can be more of a concern for paramedics than those who will head to the mountains.

"Hikers as a general rule are a little more cognizant of their need to drink liquids because that's a normal thing as you're hiking. People that are sitting down and are static or sitting still often times don't realize how much moisture they're losing and the need to drink liquids on a regular basis," said Puget Sound Fire Cpt. Kyle Ohashi.

Still, the sunshine is hard for Western Washington to resist. Eastside Fire & Rescue has seen emergency calls climb this summer, as they typically do as the weather warms.

"With that, when you include a very hot day with it, you're going to suffer from dehydration, maybe disorientation, and hopefully you brought enough stuff with you to manage that or not get to that point," said Cpt. Steve Westlake.

That means extra work for emergency crews. At Eastside Fire & Rescue, they use a special vehicle for rescues on trails.

"Our average call on a day to day basis takes a half hour to take care of. These calls take 2-3 hours," Westlake said.

Officials say heat stroke is the most serious concern. The warning sign: when someone stops sweating. That's why it's important to hydrate long before you start to feel thirsty.

"And when you lose that ability to sweat your body has no way to get rid of that heat and now we have a true medical emergency," Ohashi said.