I think it's already been said that there are several factors which can/should affect your decision. I've camped in rain and thunderstorms a number of times. It make me nervous, but accidents are rare, and depending on the location, you can do a fair amount to mitigate your risk. Most memorable recent storm was a few years ago where I was racing the rain to a state park. Got in, got set up up, started to heat up some water for dinner, and it started to pour. Nixed a hot dinner in favor of a few granola bars under my tarp and proceeded to hunker down in my hammock for the night. Thunder and lightning were pretty constant for a couple of hours. I talked myself through it by pointing out that I was camping near, but not not on, a lake, so I was in a lower lying area, but not the exposed, lakefront areas. Maybe I was fooling myself, but alternative was to hole up in the restroom for the night. But it does seems like the most severe type of lightning strike happens when a person is out in the open during a storm. In most places where I've traveled, not being the tallest thing around is pretty easy. Of course being next to the thing that is struck by lightning is also not good. But I figure if you're not the tallest thing around, and you're not under the tallest thing around, your odds are pretty good. In fact, death by lightning strike is way less common than a cyclist dying in a motor vehicle collision, which is also not that common. So my feeling is that if you're going to have to spend a lot of time out in the open, and there's a good chance of storms, think twice. And if you're going to have to be sharing the road with cars in a downpour, think three times. But if you feel like you can avoid those two situations, my technique is to wait for a break in the weather and go for it. We're currently "enjoying" a couple of weeks of daily thunderstorms. I have my "bus rack friendly" tires on my bike so I can switch to a bus commute if needed for comfort or safety, but it hasn't happened yet. The storms have blown through while I'm at work, leaving me to ride to and from work safely. Yesterday the rain came through while I was sitting in a movie theater, and I came out to find a soggy bike, but my ride home was fine. I've certainly spent my fair share of time lingering in a restaurant or hanging out in the overhang of a gas station waiting for weather to pass, but I've found that if I use the forecast to make all my decisions, I'll never leave the house, but if I use the actual weather that's happening right now to make a decision, I only occasionally end up soggy, or hiding under an awning. With the caveat that you don't want to set yourself up for seriously life threatening situations, my attitude has been to start riding when the rain stops and hope for the best.