My family has had a vacation/weekend house on a lake for a few years. One of my daughters has made our LSC's open water zones team. That meet is this weekend in Chattanooga. Weather is a threat - first race is late Friday, others are Saturday and Sunday mornings.
So my question is how you determine when to get out of the water or call off an event? In a pool, generally, if you hear thunder, you get out (and having had a tree in my yard get hit 10 minutes before the rain fell, I get why). However, on large bodies of water, the sound can carry so far, I'm wondering how you determine when you get out? During one weekend last Summer, we got out at the lakehouse when we heard thunder, but our neighbors just ignored it and kept on swimming. I'm guessing we were over cautious, and while I don't want to take chances, during this time of year, we can go on for hours upon hours hearing thunder, and never get hit. So I hate to waste any of the few days we get. Obviously, I'm also wondering what to expect for this weekend, primarily the Friday night race.
According to the CDC there on average 33 lightning related deaths in the USA each year. Around 8% of these are water related (boating, swimming, beach …); of these most are boating related. So in any given year there are typically 0 to 1 swimming lightning fatalities in the USA.
Some research indicates that lightning dissipates within 20-60 feet of a water surface strike and in most lakes it doesn’t dissipate down more than a few feet. Also water acts somewhat like a Faraday cage dissipating around rather than through objects in it. Some research also indicated that many lightning fish kills may be attributed to the sonic blast and not electrocution. And the sound waves travel much further underwater, so swimming underwater to avoid the surface dissipation is not always a good idea.
So based on current data the “safe distance” is 0 miles. However, if I’m running a race or a USA Swimming practice I’m going to use 6 to 12 miles as my safety perimeter and evacuate the water if lightning is detected in this circle. If it’s just me and a small group on training swim, we generally keep going through thunder or cloud-to-cloud lightning or cloud-to-ground lightning more than 2 miles away.
According to the CDC there on average 33 lightning related deaths in the USA each year. Around 8% of these are water related (boating, swimming, beach …); of these most are boating related. So in any given year there are typically 0 to 1 swimming lightning fatalities in the USA.
Some research indicates that lightning dissipates within 20-60 feet of a water surface strike and in most lakes it doesn’t dissipate down more than a few feet. Also water acts somewhat like a Faraday cage dissipating around rather than through objects in it. Some research also indicated that many lightning fish kills may be attributed to the sonic blast and not electrocution. And the sound waves travel much further underwater, so swimming underwater to avoid the surface dissipation is not always a good idea.
So based on current data the “safe distance” is 0 miles. However, if I’m running a race or a USA Swimming practice I’m going to use 6 to 12 miles as my safety perimeter and evacuate the water if lightning is detected in this circle. If it’s just me and a small group on training swim, we generally keep going through thunder or cloud-to-cloud lightning or cloud-to-ground lightning more than 2 miles away.
