Lightning strikes the Gateway Arch on August 27, 2014
The Short Answer: The Gateway Arch is struck by lightning only once or twice in the average year.
The Long Answer: Some online sources say the Arch is struck hundreds of times a year, but this is not true in reality. I have been intensively covering St. Louis storms since January of 2010, focusing most of the time on the Arch (here is the gallery of photos from that effort). I didn't capture the Arch getting hit until August 27, 2014! Granted, while I cover 90% of St. Louis storms, I inevitably miss a few here and there - so it's possible that prior to August 2014, I've just been very unlucky. I know of at least three other Arch strikes that I missed, in 2011 (that video is on Youtube), another on April 10, 2013 and the most recent on July 25, 2016. However, it's conclusive from direct observation that the Arch is not the crazy lightning magnet that one might first assume.
First of all, the Arch does certainly have a much higher probability of getting hit by cloud-to-ground (downward moving stepped leader) lightning in any given storm, that is, compared to other buildings and objects in the city. At 600 feet tall, all it needs is a stepped leader to descend within 600 feet or so of it, and the channel will likely connect to the structure. However, it appears that this might happen only once or twice a year (at best). The number may even be more like once every two years - particularly if the 2 to 3 storms a year I miss are like the other 10-15 per year I do observe.
As for upward (ground-to-cloud) lightning, the Arch is barely tall enough to initiate an upward lightning stroke (600 feet is very near the bottom of the height scale for towers to be good lightning leader initiators). I have observed and photographed many strong electrified stratiform lightning events over the Arch, none of which initiated even a short lightning leader from the structure. It could be that the Arch's curved profile doesn't allow for a focused "point" of electric field concentration like a tower antenna tip does. Or, it could be that the abundance of tall buildings nearby regionally distributes the EF buildup enough to prevent leader initiation. Whatever the cause, I can say with confidence that upward lightning strokes from the Arch are extremely rare (possibly less than once every 3 years or more).
A good case for Arch strike rates was on June 26 of 2011, when continuous thunderstorms raged over downtown St. Louis for several hours straight. I was there the whole time with cameras (still and video) on the Arch (having to stop to recharge camera batteries twice), and it was not hit! The closest a bolt came was this one, with not even a small leader initiated from the Arch itself:
Then there were these two storms (September 18, 2010 and August 4, 2012), two of the most lightning-active I have observed over downtown in the 4 1/2 years I've lived here. No Arch hits during those either, not even a leader (both of these images are 8-frame stacks of multiple strikes):
I have even more videos of St. Louis storms with no Arch strikes - this is a compilation of a half-dozen of the better lightning events over the city I've captured. And those good lightning events over the city themselves are quite rare - with most of my storm shoots in the city, I either captured no good lightning worth saving, or the storm didn't produce visible lightning at all (entirely within the clouds). Photogenic lightning over downtown is quite the rare event - maybe 3 or 4 times a year. My point being, only during the most insane barrages of cloud-to-ground lightning right over downtown St. Louis does the Arch stand a good chance of getting struck. That type of storm is not common anywhere - I chase storms all over the country and see such a barrage maybe once or twice a year!
I'm only aware of two videos on the internet (other than the one I captured in August 2014) of the Arch being hit by lightning, one from 2005 and another from 2011 (the one that occurred while I was out of town). The only still image of an Arch strike I know of is the one captured on April 10, 2013 by Brad Krischel. As a national landmark in a large city, the Arch is usually covered by at least one or two photographers during your average storm (probably more today thanks to cell phone video), and I think a lightning strike event to it would not go unpublicized (unless the photographer was never inclined to share his capture with anyone).
So, to sum all of this up, based on my personal observation over 4 and a half years (as of today in August 2014), I estimate that the Gateway Arch is hit by lightning only once or twice in the average year. I believe that there are some years when it is not hit at all! I'd maybe go as high as 5 times in a more active thunderstorm year - nowhere near the figure of hundreds of times a year.
Is it safe to be in the Arch when it is struck by lightning?
Yes. The Arch is a well-grounded steel structure. Lightning current from a direct strike flows harmlessly through the structure to the ground. Anyone in the observation deck at the top, in the trams, in the museum below or even standing next to it would not feel a thing! The thunder is quite loud and startling, however!
The exception might be that someone standing outside at the base of one of the legs while touching the structure *might* feel at least a mild shock at the time of a strike. However, again, since the structure is well-grounded, it's doubtful such a shock would be lethal. I'm not aware of anyone who has experienced that - but I wouldn't want to volunteer to be the first!
Events mistaken for Arch strikes
I have seen at least two high-profile images/videos (making the rounds on news broacasts and social media) incorrectly claiming to show the Arch being struck by lightning. One of these is from May 30, 2013 in a video taken from Busch Stadium. In that particular video, you can see the lightning continue on down past the top of the Arch, clearly hitting something behind it. I was storm chasing in Oklahoma that night and was not present for that storm.
The other video I know of is from September 2012 taken from the Millenium Hotel that, again, shows a lightning bolt striking behind the Arch (hitting the Eads Bridge) but claims that the lightning hit the Arch. I was actually shooting video below the Arch on the riverfront for that particular storm, and witnessed the strike to the Eads - no bolt hit the Arch.
In both of these cases, the common factor was that the main channel of the bolt clearly goes behind the Arch. You can inspect for that kind of thing for any future events to determine whether there was actually a genuine direct hit.
The following comments were posted before this site switched to a new comment system on August 27, 2016:
The Arch got struck by lightning last night (April 10th, 2013). Did you happen to catch it? - Posted by Kyle from St Louis
Kyle, I missed it by 30 seconds. I was there but didn't get set up in time. - Posted by Dan R. from New Baden, IL
when will the time capsual be opened - Posted by Brenda Satterfield
Hi Dan, Having grown up in Alton, Ill., I'm glad to see someone as interested in the weather there as I am. St. Louis is, IMHO, the nation's best kept secret in terms of a Cool place to live and work and visit. Keep up the great work, Dan. Cheers, Larry - Posted by Larry Mager from Fairborn, Ohio