lightning can make blue fire shoot out your outlets.
unplug.

yeah, if you get a hit from lightning, that surge protector isn't going to do a damn thing.

We don't want to lose our precious Harvey Girls!

I think both answers are right. The chance of a lightning storm ruining your equipment is small, and probably covered by insurance. A direct hit to your house won't have you caring one whit about the recording equipment -- it'll be your own life first and foremost. So continuing to use electrical equipment can make good sense, especially if you live somewhere where lightnings storms are very common (you could be down half the summer in the Midwest).

More than 99% of the time, you'll get away fine using electrical equipment in a lightning storm, simply because lightning effecting your area severely is rare.

But, a surge suppressor won't work against a lightning-induced surge if the strike is near your house (say it hits a transformer a block or two or 10 away). The current in those situations may very well be enough to make the supressor useless. To further cause problems, a (very) nearby strike can even destroy unplugged equipment -- the electrical cabling can pick up an induced signal and create enough current to fry sensitive stuff, even if it was unplugged, if say, lightning took out your neighbor's house.

They make whole-house surge suppressors that look like a breaker in the breaker box. Except in the case of a direct hit, these will generally protect your stuff from a nearby lightning strike into the electrical system. They might even work in a direct lightning strike, but they won't protect against fire: if lightning hits your house everything is useless. You still need a regular surge suppressor, though, for PCs and such.

I think at the end of the day, you should just buy insurance and not worry about it. Unplugging stuff may save your gear, but it's not going to do it very often. And a direct hit to your house will kill everything, regardless of whether or not is plugged in. The hit that doesn't destroy your house but does destroy your gear (that is, a hit into the electrical distribution system relatively near your home) may destroy gear in use, but it's going to happen pretty rarely.

A surge protector should absolutely not be thought as protection from a nearby or direct lightning strike. It's not and it won't. A surge protector protects your equipment from, well, a milder surge of electricity that can be caused by a variety of things—a more distant lightning strike is one of them. But usually I think it's distribution problems of one sort of another.

Leaving the equipment plugged in but turned off cannot be relied upon to protect equipment from a direct or near lightning strike because both the mechanical switches and electronic switches that make the equipment be "off" are basically no barrier whatsoever to the kind of current you'd get from lightning. Unplugged, obviously is basically perfectly safeguarding the equipment.

I've heard that heavy-duty, quality uninteruptable power supplies might protect against lightning damage, but it's hard to see how that is. It's probably best to think of those as much better surge protectors in this context. They won't safeguard the equipment.

But, you know, what's most relevant here is the probability of a direct or nearby lightning strike. If you can more accurately assess that, then you'll know when you need to unplug and when you don't. Aren't there real-time lightning maps possible these days and don't the TV news stations use them? It'd be cool if you could see your area via the web.

It depends a lot on the severity of the storm.

If you want to save your equipment, unplugging it protects it from spikes/surges and brownouts on the grid as the lightning storm causes havoc on the electrical grid.

But having a good UPS and surge protector can help mitigate (but never eliminate) the risk from "unconditioned" commodity electrical power. Though, a UPS may effect the performance and signal/noise ratios of sensitive analog gear.

If the storm is sudden and severe and extremely local, running around and unplugging gear is probably going to kick up your personal risk factor a few notches. Probably not as much as walking out on a golf course and waving a 20 foot piece of rebar around, but it'll increase it plenty. I've seen plenty of warnings to stay away from phone lines, power outlets, pipes and other metallic/conductive channels (even when indoors) during severe electrical storm activity.

If the concern is trying to protect gear from direct strikes, well, good luck. You're talking about a few million amps that may have just leapt across miles and miles (or hundreds of miles) of open air. Lightning can still get inside an unplugged device and melt it into slag. If lightning hits your house or building, hopefully it'll get diverted by the electrical or water pipe system to the ground tap. It can still branch out and melt stuff and otherwise behave unpredictably.

A surge protector won't help, neither would a UPS. It's just going to arc around all the nice conductive bits and fuse them or vaporize them anyway.

So, yeah, unplugging helps in that A) It primarily protects your from power surges and brownouts, B) It makes it that much less likely that you'll get a direct strike flowing through the equipment.

But in doing so you're probably increasing your own life and limb risk

To further cause problems, a (very) nearby strike can even destroy unplugged equipment -- the electrical cabling can pick up an induced signal and create enough current to fry sensitive stuff, even if it was unplugged, if say, lightning took out your neighbor's house.

That's a good point that I wasn't aware of. It's basically very small, localized EMP. I think it'd be only very sensitive equipment, probably, and I'd also wouldn't be surprised that many buildings are effectively a Faraday cage.

As to the thing about lightning hitting your house—if that's a real concern, get a quality lightning rod and have it installed by an expert. I had a friend who was an atmospheric physicist at Langmuir labs where they do the triggered lightning experiments, became an expert on lightning rods, and works for the industry now. He always said that a good lightning rod eliminates most of the danger of being struck.

Unless I'm misremembering. But I don't think I am.

This discussion reminds me of something weird and cool that happened when I was a teenager.

The whole family was in the living room watching TV, if I recall correctly (though, like most teenagers I didn't spend much time with the family like that, so I may be misremembering). There was a very close lightning strike. Very startling and dramatic.

Then after about five or ten seconds, suddenly something changed. It was hard to figure it out at first. Than it became noticeable: the lights were getting brighter and the refrigerator pump was running faster. And we could hear a loud humming noise coming from outside the house. The lights get brighter and stuff was almost mythically intense, like something out of a movie. My dad and I ran outside because of the noise and just in time saw the transformer on the pole in the alley behind our house explode. I really did explode. Not super-violently, but an explosion nevertheless. I can't recall if I knew enough then to be concerned about burning PCB's.

Thanks so much, everyone. This question's become more pressing since someone (believe it or not) donated us a much, much nicer mixing board than our current one, which is crapping out.

Thanks to your advice, during storms we'll probably curl ourselves around it like cats. And yeah, it storms a lot here, esp. in spring and summer, so if you need us, you'll probably find us in the closet in the fetal position.

Get a UPS. They sell 'em at Staples, relatively cheap, too.

a long time ago, a storm fried an old Toshiba laptop of mine, a T-1000

I loved that machine