PHOENIX -- Emergency workers are warning valley residents of the high potential for heat stress this weekend.

“So many people take this lightly and you can't,” said hiker Bob Snyder.

Even Snyder admitted that noon is not the best time to hit the hiking trails, but he did anyway on Thursday.

“I enjoy the hike and you can if you know your limits,” said Snyder. “Few do and they don’t survive.”

Snyder, 75, said he brings a cool, wet cloth with him on his hikes to keep him cool.

“This is what every hiker should have, it’s lightweight, you can breath through it, keeps the dust off of you and it’s like a cooler,” said Snyder.

Phoenix Fire Captain Hugh Chase said the number of heat-related emergency calls at just nine days into July is about 75. The whole month of June had 80 calls.

Chase said the early signs of heat stress begin with heat cramps, when there’s muscle pain and possibly some twitching.

The next level is heat exhaustion, which usually happens after you’ve been out in the sun for too long, without enough water and you start to feel sick and look pale, but might still sweat.

If left untreated, it develops into heat stroke, where you’ve likely stopped sweating, and can be deadly.

“Once you feel like you notice the early signs, you can take care of those on your own, get in cooler atmosphere, get in the shade,” said Chase.

Dr. Kevin Rodriguez at Maricopa Medical Center said that no one is immune from heat-related illnesses, but it can affect some groups more.

“Infants and elderly are the most prone of the population,” said Rodriguez.

Hiker Dan Salley, who said he was born and raised in the Valley, says he’s used to the heat.

“If you’re from the Midwest or the east, I wouldn’t even suggest even walking around this town this time of year,” said Salley, laughing. “I’d stay by the pool.”