For those that claim radon, three things:

- Watch the decay rate. A fast decay doesn't necessarily mean radon either. Some of the decay rates seen are relatively fast but the certainly don't match up with radon decay. Some of them do - these are probably radon. But that doesn't explain most of what people have been seeing in the rain.

- Do not forget that radon is a product of none other than uranium. It's now been acknowledged that Fukushima jettisoned quite a bit of uranium into the air. If you've found radon, it may be from that, not from below you. You'd have to piece together other factors: Are you in the jetstream path, collecting possibly contaminated rain? Is there radon decay rates in there - AND some other stuff too? Or, is it's just radon - pretty consistent - and inside your basement floor?

- Radon is an alpha emitter. Most geiger counters, for example, Soeks, can't test for alpha emitters. Only a select few, quite expensive and fragile ones, that have mica windows/pancakes can. If a geiger counter that doesn't have a mica window/pancake on it is picking up something radioactive in the rain, it ain't radon!