This 5-minute data is logged using a Raspberry Pi3B+ connected to a MightyOhm Geiger Counter kit located in East Vancouver, WA, US.  This geiger counter kit uses an SBM-20 tube to detect radiation.

What is a normal background/naturally occurring radiation exposure rate?  Varies depending on where you live.  Click the values for the sources of the data.

Average across the U.S.:   0.34μSv/hour
Global average:                 0.17-0.39μSv/hour
Average for station region: 0.05μSv/hour (EPA Portland Station)

What is the US average for accumulation per year of background/naturally occurring radiation?  3.1mSv  Based on current rates measured at this station, an 'Annual Equiv mSv' value is displayed in the lower right corner of the graphs below.  The location of this station has historically measured below the global and national average.

How do different environments, activities and event exposure rates compare?  See this Radiation Dose Chart by XKCD.