Rain storm during calibration spectrum

[Geoff]

It was a normal cloudy August day here in Anchorage. I setup my spectrometer with a Na-22 source for calibration, then left for the day to run chores and what not. While I was gone some rain fall. My count rate vs time shows a 13 counts per second increase shortly after the rain started, from 218 cps to 231 cps. The extra activity peaked at 235 cps and after 8 hours has fallen back to around 220 cps.