Here is the current Radiation Levels at my work desk at home:
Sammamish, WA, USA
CPM => Clicks-per-Minute. 1 CPM is equivalent to 0.001 mR/Hr

This graph shows normal background radiation. At my location, this normally runs in the 10 -> 18 CPM range, with “bursts” up into the low 20’s at times. Anything above 40 or so would indicate some sort of radiation event taking place. Long term exposure at those levels or higher would not be good.