BOSTON (CBS) – Many spent Saturday lounging by the water, but some kept up their daily workout routine along the Charles River.

In Boston and elsewhere, officials urged the public to take it easy as temperatures reached into the high 90s. As of Saturday night, Boston EMS reported that over Friday and Saturday they had transported 12 people with heat-related illnesses to the hospital.

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Some headed to the water fountain on the Rose Kennedy Greenway to stay cool.

As one 5-year-old said, it was hot, so, “I went in the water, then I got cold.”

One tourist from New Jersey said he took it slowly during the day, he said. “Hit the pool this afternoon … try to do a little indoor stuff at the peak of the daytime … stay hydrated.”

That’s a lot like the advice officials are giving.

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“We’re kind of in a high alert right now. I don’t like to beef up the fact – we’ve had heatwaves before. But this one does seem a little more out of the ordinary as people were talking. So we’ll take every safety precaution possible,” Boston Mayor Marty Walsh said. “We’re asking people to be careful if you’re out; drink plenty of water.”

Sunday is likely to be a scorcher, too, so the Jimmy Fund was forced to cancel this year’s 5K run, which was supposed to happen on Sunday.

“It was a difficult decision, but just given the heat and the humidity that’s predicted for tomorrow, we just knew we had no other choice. We want out runners, our volunteers, our sponsors, our vendors to be safe,” said Suzanne Fountain, Jimmy Fund vice president.

In Sudbury, Patriots star Julian Edelman was busy with his youth football clinic – and keeping the kids cool and hydrated was a top priority.

“Extreme, extreme hot conditions,” Edelman said, “But we’re keeping them all watered up and enjoying it, so it’s fun.”

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Signs of heat stroke include feeling dizzy, a faster pulse and not feeling well or feeling nauseous. To stay ahead of these symptoms, hydrate first thing in the morning and throughout the day.