Signs To Look For When Determining If A Hot Spring Is Safe To Swim In

Forget hot tubs and luxury spas. There is nothing quite like having a soak in the warm, restful waters of a hot spring, surrounded by beautiful nature. Most natural hot springs arise in volcanic regions where rainwater, groundwater, or snowmelt are heated by molten rock (magma) just beneath the surface. Occasionally, the hot water bursts from the ground to form dramatic geysers, but more often than not, it forms pools of heated water containing therapeutic minerals. Hot springs are usually located in places of great natural beauty, and some are safe to swim or bathe in.

The U.S. is home to several world-famous swimmable hot springs, among them Glenwood Springs in Colorado, the largest mineral hot springs on the planet. Lesser-known gems include the stunning free-to-visit Remington Hot Springs in California's Sequoia National Forest, which features three artificial pools overlooking the Kern River. While hot springs can be safe for humans to bathe in, others can be perilously hot or contain dangerous bacteria, so it is very important to check for specific signs before you swim. Here's what to look out for.

There are many benefits to soaking in a hot spring, including relaxation, pain reduction, and improved skin, but none of these are worth getting scalded, or even worse, risking your life. The hottest springs in Yellowstone National Park, for example, can reach a scorching 345 degrees Fahrenheit. The most famous is Excelsior Geyser in Yellowstone's Midway Geyser Basin, which is a stunning shade of brilliant, deep blue, but definitely not safe to swim in. In fact, more than 20 people have died from burns they suffered after they either fell or intentionally entered one of the springs at Yellowstone, highlighting how dangerous it can be.

Before entering any hot spring, especially a natural one, do some advanced research to check if the temperature is safe to enter, or even use a thermometer to check yourself. There may also be signs close by indicating the estimated temperature of the water. Never assume that the temperature of a hot spring is inherently safe; always do your due diligence. Some people have a higher tolerance for heat than others, but even if you love a hot soak, staying too long in the water can risk raising your body temperature and put you at risk of heat stroke.

When it comes to safety, natural hot springs are where you need to keep your wits about you, as they are a product of the natural world and therefore come with more risk and unpredictability. You should never enter a natural hot spring without doing your research first. Commercial hot springs, on the other hand, are developed around a geothermal water source, specifically designed to be safe for humans to enter. Quite often, they come with a lot more convenience, such as changing rooms, spa treatments, and even fine dining options. The only thing to be mindful of is that hot springs of any kind are not recommended if you are pregnant or have a relevant preexisting health condition.

There are certain etiquette guidelines that apply to any type of hot spring you visit, whether commercial or natural. Hot springs are a place of quiet and relaxation, so it is recommended to keep noise to low levels and be respectful of others' privacy. For natural springs especially, it is very important to leave no trace and avoid using skin or hair products that are not biodegradable, as these can be potentially harmful to wildlife and the wider environment. Hot springs have been used by humans for millennia, and deserve to be preserved for future generations.

Pay attention to water clarity and the smell of a thermal pool, as this can indicate if there are any harmful bacteria or algae present. If the algae bloom, they can release toxins that can be dangerous for both humans and animals. Slow-moving water or still water is particularly susceptible to harmful algal blooms. If the water is looking discoloured or if the surface appears to be scummy, it is recommended not to enter.

Equally, if the water is producing an unpleasant smell, you should be wary. That being said, some natural hot springs can smell like rotten eggs due to the presence of sulphur, and this isn't a bad thing. These minerals can actually be good for your skin and general health. The best thing to do is check online in advance to see if there have been any advisories posted about the status of the hot spring. This is also important so you can ensure the water does not contain any harmful parasites.

It may seem obvious, but if you see a sign near a hot spring warning you not to enter, you should take that at face value. Alas, this advice has been ignored at times, with fatal and grim consequences. In July 2022, 70-year-old Il Hun Ro entered the Abyss hot springs pool in Yellowstone National Park, and his foot was discovered floating in the spring the following month.

And it's not just the high temperatures that can pose a danger — animal predators, parasites, and unstable ground may also put you at risk of injury and an unwelcome trip to the ER. It's also wise to keep to the paved paths (if they exist) to reduce your chance of slipping and falling. If nothing else, following local guidelines will save you the embarrassment of a lawsuit, à la Pierce Brosnan. The former James Bond actor pleaded guilty in 2024 and was fined $1,500 for hiking off-trail near one of Yellowstone's geothermal pools.