SIOUX FALLS, S.D. (KELO) — At the time of writing this sentence, it is 85°F in Sioux Falls. While that makes for a beautifully warm and sunny day on land, below water is another story.

Across South Dakota, temperatures in rivers and lakes have yet to reach safe swimming temperatures.

Using sites such as lakemonster, we can see that lakes across the state are hovering in the 40s, 50s and 60s. Likewise, the National Weather Service tracks water temperatures along the Missouri, where we can see it sits at 41°F at its coldest point in South Dakota currently, and just 61°F at the highest.

When it comes to water temperatures, too cold may actually be warmer than you think, according to Thayne Munce, Sanford Research assistant scientist. “You lose heat through water much more rapidly than you would in air,” he said.

What this means is that even water temperatures in the 60s can be cause for concern, with rapid loss of body heat.

Munce says that the time you spend in the water can be more important than the actual temperature, noting ‘polar plunge’ type events as examples that brief dips in cold water can be relatively harmless. “But if you stay in 50° water for an extended period of time, you put your life at risk,” he said.

If you were to take a plunge into water that’s in the 50-60° range, Munce said you may experience an immediate cold-shock response. “You’re gasping for air; you’re gonna be hyperventilating,” he noted, adding that this could induce panic in some.

While water in the 50s and 60s is cold, Munce says you likely wouldn’t succumb to cold immediately, but spending longer in the water could lead to greater issues.

Long term exposure to colder waters can result in hypothermia. “You can lose consciousness and die, but before that happens muscles are going to start to deteriorate — so in a situation where you may need to swim yourself to safety, you can be compromised,” Munce said.

While something like hypothermia and its ensuing symptoms may not occur immediately, Munce said it could occur within a timeframe of about half-an-hour to an hour or more depending on the person.

One sign that the water your swimming in may be too cold is that it feels too cold. “That’s a key indicator,” said Munce, adding that we’ve likely all had the experience of jumping into a pool and feeling like the water is ice cold, though in those situations, you general get acclimatize pretty quickly.

“If you’re not getting that — if you’re in the water for 30 second or a minute and you begin to shiver — that’s a pretty good indicator.”

So when is it safe to swim? Munce mentioned 70°F as the point at which temperatures below that mark can be dangerous, though he noted that even 70° will likely not be comfortable to swim in, “but below that, you’re going to see some rapid heat loss from the body,” he said.

While there is little risk, temperature wise, to things like wading in the water or dipping your feet, Munce advises never swimming in open water alone. “Have a buddy with you,” he said, noting that it’s not just temperature, but things like cramps and other factors that could make it suddenly difficult for you to swim.

In addition to pairing up, you should also have a floatation device present and understand your limitations, both in terms of your swimming ability and the temperatures that you’re used to swimming in.

“Use common sense, be smart, use the buddy system, know your limitations, be aware of your surroundings,” Munce said.