But what if you are halfway home and it starts raining?

I am wondering how "I use an umbrella" can not be an obvious response. I guess you just never heard of them.

Is there some subtle trap I am falling into?

My thoughts too. It's not too hard to carry one, although I have had to buy one at work once or twice. I like walking in the rain - it's the really hot, humid days that are the worst. I just walk a lot slower on those days. Trees or shade from buildings is good on those days.

Umbrellas are great for a mild sprinkle. In a real downpour, they are really only good for a quick dash from one doorway to the next, and even then you are still likely to get soaked below the waist. Not to mention that carrying a metal pole in the air whilst you are wet and thus conductive is not the wisest of ideas during an electrical storm.

Most downpours are relatively short term affairs, lasting 10-20 minutes or so. Most people will wait them out in a doorway or other shelter if they possibly can, then deploy their umbrellas once the rain has tapered off to a mild drizzle.

"worried about being struck by lightning"

Oh come on, that is a really lame excuse!

If we are using this sort of excuse ("I'm worried about getting a bit wet occasionally") what chance is there of getting car drivers out of their Faraday cages?

In a dense urban environment, with lightning rods common, the risk at street level is minimal. Less than running to the barn.

Alan

Build COVERED sidewalks with some of the money we save not building roads and with some of the road material we tear up to get farmland back. I learned that from the Ray Swangkee city-states-of-stone idea. In a society that travels mostly by walking, this would be worth it to protect from the heat of the sun, the annoyance of the rain, and the danger of lightning. Until then, have a plastic poncho in your backpack

Overhanging balconies add space for residences and shield walkers below (although not perfectly).

Some years ago, New Orleans outlawed new overhanging balconies, but this is not being challenged.

Best Hopes for a dry spot in an afternoon thunderstorm,

Alan