Hurricanes, also known as tropical cyclones and typhoons, are large, spinning, low-pressure weather systems with high wind speeds. They form over warm, tropical or subtropical waters, like the Atlantic basin, the eastern North Pacific Ocean, and occasionally the central North Pacific Ocean.

Hurricane Florence making landfall near Wrightsville Beach, North Carolina in 2018. Photo by NASA Johnson

Hurricane season falls from June 1 to November 30. These fierce storms cause damage to natural environments and property, and can be fatal to both wildlife and humans (especially recreational water users).

Here are four things you should keep in mind when swimming during hurricane season

1. Storm Surges and Storm Tide

Storm surges are atypical increases in wave and water levels due to powerful storm winds, such as those of a hurricane, pushing water to the shore. Storm surges may cause coastal flooding and be deadly to those both near and far from the shore.

Storm surges happen quickly and without much warning.

Storm surge in Porthleven, Cornwall. Photo by Tony Armstrong-Sly

They are particularly dangerous in harbours and bays. If you see the water pull far away from shore, it may be moments from quickly coming back in far up the shore. When this happens, it’s a good idea to quickly get out of the way. Get as far away from the beach as you can, and get on the highest ground possible.

Storm tides happen when storm surges combine with the regularly occurring tide. Storm tides cause an extreme rise in water levels.

Storm tide in Oslofjord, Norway during hurricane Dagmar. Photo by Bernt Rostad

Together, strong wave and water action can erode coastlines. A single hurricane is able to clear away beaches and sand dunes. A beach may look very different (or may have disappeared entirely) when you head to the shore after a severe storm. Always use caution when walking on beaches after a hurricane, as erosion may have made the shore unstable.

2. Rip Currents

Hurricanes generate extremely powerful winds. Hurricane winds create big, strong, dangerous waves that can be over 18 meters. Rip currents happen when violent winds push the water in the ocean against the shore. In fact, rip currents in an area sometimes mean that a hurricane is near. Even waves breaking far away from the hurricane itself can form fatal rip currents.

Photo by Eliya

These channels of water trap and suck even experienced swimmers out to sea. To escape a rip current, swim parallel to the shore (rather than towards it) until you no longer feel the current’s pull.

Even if there is not a rip current or storm surge present, waters can get extremely rough when a Hurricane is nearby. In Barbados in 2017, a teenage professional surfer died surfing waves caused by Hurricane Irma.

3. Changes in Water Quality

It’s not only the water itself that poses a threat to people around hurricane season, but also what’s in the water.

Hurricanes sometimes cause coastal flooding, and floodwater often contains metal or glass fragments and other sharp objects that can puncture the skin, power lines, and other dangerous debris. When injured in the water, your body is exposed to whatever contaminants are present.

Photo by Chesapeake Bay Program

In addition to the visible hazards that may be in water following a hurricane, invisible hazards may be present as well.

During hurricane season, all kinds of pollution enters the water. When Hurricane Katrina hit the U.S. in 2005, 575 spills of petroleum or hazardous chemicals happened and over 350,000 automobiles leaked gasoline and toxic fluids into flood waters, totalling about 10 million gallons of oil that entered the New Orleans Area Watershed.

Aftermath of Hurricane Florence in North Carolina in 2018. Photo by North Carolina National Guard

When there is heavy rainfall, combined sewer systems can overflow, spilling untreated stormwater and sewage into waterbodies. A hurricane’s strong winds can also unsettle any pollution that is at the bottom of waterbodies.

When Hurricane Florence hit North Carolina in 2018, the heavy rains caused runoff from huge pig farms to bring staggering quantities of fecal matter to surrounding areas.

Photo by North Carolina National Guard

Even if the water looks clean after a hurricane, it frequently contains bacteria, pathogens, chemicals, and nutrients capable of making people very sick. It’s a good idea to wait at least two days to swim after heavy rainfall, and you should wait even longer after an extreme weather event like a hurricane.

4. Algae Blooms

At times, heavy rainfall during hurricanes leads to stormwater runoff, sewer overflows, and flooding. In turn, this brings excess nutrients into waterbodies, which can cause algae blooms. When certain algae blooms die off, they release toxins that make people sick from coming into contact with the water.

Photo by Dru!

After Tropical Storm Gordon in 2018, the red tide in Florida intensified and spread to the Florida Panhandle. This harmful algae bloom can kill marine species, and threaten the health of humans, too. You can check the current status of Red Tide in Florida here.

Rising sea levels and warming sea temperatures are expected to exacerbate the effects of hurricanes, so it’s important to know how to stay safe during hurricane season as our climate changes.

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