The sun beats down and the air is heavy with humidity, but that doesn't slow Isabella Lucia as she laughs, sprints and kicks the ball during soccer practice.

Suddenly a whistle blows.

With one shrill note practice is over — shut down early because of the heat.

The seven-year-old jogs off the field and pours an entire bottle of water over her head, joking to her teammates that it makes it look like she's been sweating a lot. She loves soccer and doesn't mind playing in the sun but her mom Amanda, who's working double duty tonight as her soccer coach, wants to make sure her players stay safe in the sweltering summer temperatures.

"It's just a little too much for these guys in the heat," she explains. "We just try to accomplish something, have some fun then send them on their way."

But just how much kids will be able to accomplish while playing recreational sports or attending summer camps in coming years is a question increasingly being considered by athletic organizations and camp leaders across Canada in the face of heat waves climatologists predict will become more frequent and more intense with climate change.

Amanda Lucia works double duty as both a mom and her daughter's soccer coach. (Dan Taekema/CBC)

When it comes to hot summers, Dave Phillips says Canada hasn't seen anything yet.

Phillips is the senior climatologist for Environment Canada, meaning he studies both the opportunities and threats climate change will present.

"People won't recognize the climate in 40 years. It certainly won't be like anything is right now," he said.

"One of the easiest things to suggest in an altered climate is the fact that extremes of heat during the summertime will be much more than we're used to."

Models suggest coming years will bring longer heat waves that are more "torrid and intense," along with more unpredictable weather in all seasons.

Scientists typically use the 30 C mark as a threshold for hot, humid days that are considered unhealthy.

"If we look at the Hamilton-Toronto area we typically get now about 16 days a year when temperatures would be at or above 30 degrees," Phillips explained. "But we see by 2050 ... it would be more like 50 days."

Environment Canada climatologist Dave Phillips says the Hamilton-Toronto area could see as many as 50 days with temperatures of 30 C or higher by 2050. (Jason Viau/CBC)

By the end of the century, the models show that number could hit 77 — more than two straight months of temperatures of 30 C or higher, with humidex values in the 40s or 50s.

Kids can warm up faster than adults

Those scorching temperatures raise questions about safety, especially for kids attending camps or playing sports under the sun. It doesn't matter how healthy or athletic a person is, any body can be stressed by overworking in a hot situation, Phillips said, pointing out even an NFL player died of heatstroke after practicing in humid weather.

That matters because, compared to adults, young children have even fewer tools to stay cool, according to Dr. Brian Timmons, Canada Research Chair in Child Health and Exercise Medicine.

He says, before puberty, kids generally don't sweat as much as teens or adults. Instead, they have to rely on things like conduction — heat loss from the body — to cool down, rather than the evaporation of sweat. That's tough to do, especially when it's humid.

We're seeing more and more … water breaks exercised during the intense weeks of the summer months. - Johnny Misley, Ontario Soccer

All of this means kids can potentially heat up faster than adults.

Heat illness can lead to long-term health problems or even death, though most of its effects are temporary.

Sometimes it causes victims to faint or collapse. Dizziness and headaches are other signs someone should slow down and rest, said Timmons.

Parents and coaches should keep an especially close eye on younger children in the heat, according to the doctor, who added rest and access to fluids on a regular basis can help keep them safe.

And, in some cases, cancelling camps or sports outright might be the best option.

"I get the competitive nature but ... it's not the end of the world if we cancel a few things because it's too damn hot outside," said Timmons.

Soccer organization trains refs to beat the heat

For organizations with a focus on encouraging kids to stay active, cancelling games isn't ideal, but it is an option the Ontario Soccer does utilize when the temperature and humidity creep up during the summer months.

The sport organization includes more than 600 youth and senior soccer clubs across the province and relies on training for match officials to keep players — about 85 per cent of whom are under the age of 18 — safe and healthy.

"The impact of climate change … is part of their ongoing training and the greatest area they deal with is how to manage a game when it comes to heat," explained CEO Johnny Misley.

Soccer players practice and play at Ancaster High School on a sweltering summer day. (Dan Taekema/CBC)

Another tool referees rely on is multiple water breaks to give players a chance to catch their breath and cool down.

"We're seeing more and more … water breaks exercised during the intense weeks of the summer months as well as seeing the impact of what's happening on those athletes when it comes to heat exhaustion," Misley added.

Ontario Soccer isn't the only group making more and more concessions to high temperatures.

Camps see increase in hot weather alerts

Janine Gaunt, a recreation manager for Hamilton, says the city has noticed heat alerts become increasingly frequent in recent years.

Hundreds of Hamilton kids participate in city-run camps every year. When the temperatures go up, organizers can adjust the day's programming to make sure kids stay cool. (City of Hamilton/Twitter)

There are eight-day camp locations across the city, attended by 50-100 children every week. Then there's the Supie program — a free drop-in initiative for kids age six to 12 at local parks across Hamilton.

When the mercury rises, Gaunt says camp leaders react by taking the following steps:

Modifying activities to make them less active.

Adjusting schedules so kids are outside in the morning, but head inside during the hottest part of the day.

Making sure day camps have access to a pool where kids can cool off.

A clear list of strict rules for camp leaders to follow in extreme heat is something Phillips says he expects parents will start adding to their list of criteria when considering what camps to send their kids to in the future.

"Their choosing of whatever camp they go to might very well be [based on] how that camp will deal with those hot torrid kind of days that will certainly be part of the climate picture in the years to come."

Amanda Lucia is all about keeping her kids active, but hot temperatures already have her keeping them out of camps so they're not too tired to play sports on summer evenings. (Dan Taekema/CBC)

As a mom and soccer coach Amanda Lucia is all about keeping her kids active, but heat is something she can't ignore any longer.

"It's a concern for us now. Our kids don't want to do camps anymore because it's too hot, they get too tired … they're almost too tired by the end of the day to do any activities or sports," she said.

"I think there needs to be a lot more opportunities for indoor camps for kids."

This story is part of the CBC series Footprint examining climate change issues and solutions in communities across Canada. For more stories, visit: cbc.ca/Footprint.