Here is a copy and paste the Alerts section of RadiationNetwork.com:
The Radiation Network has a contributing Monitoring Station located in Grand Rapids, Minnesota that is triggering Radiation Alerts as I write this, since about 1:00 P.M. local time. Until we receive feedback from the station operator, we have no reason to believe this is not a genuine detection of elevated radiation levels, and so as with our policy, this will be allowed to play out for the time being.
The graph shows steadily rising radiation from a normal background level of about 40 CPM, eventually exceeding the 100 CPM alert level on our network. We know Grand Rapids operates the PRM-9000 Geiger counter which is built around the same ultra-sensitive pancake style Geiger-Mueller tube as in the Inspector line of instruments. Without yet knowing the source or nature of the Grand Rapids radiation, I can say that particular model of GM tube has demonstrated at other times and across other monitoring stations how sensitive it is to passing radioactive weather patterns, even from an indoor monitoring posture. When we obtain more information, we will provide a follow-up report.
For future posterity, here is a video by MissingSky101 of the high reading: