This is the current map from the Radiation Network web site. It has a couple relatively high readings in the Great Plains right now; one in western South Dakota and two in northern Colorado -- and scattered around them are readings in the 40s, along with some very low readings.
This is a current screen shot from weather.com's "weather in motion" time lapse map. Note the two bigger masses of clouds over the Pacific. The lower one is just rolling in place, but the upper one is moving quickly from east to west, i.e., from somewhere around Japan, across the Pacific, up into Canada and then down across the US Great Plains.
See it here live:
That address will take you to the default view, of the US. On the left you can adjust the map to the "world" view. Across the top you'll find the "clouds" button.
The Radiation Network, shown in the top map, is made up of volunteers who have their geiger counters on and hooked to their computers, which are connected via the internet to the company that maintains the site (which also sells geiger counters - see links at bottom of Radiation Network page.)
I have a geiger counter made by that company, but the software you need to hook yourself into the network doesn't run on my Apple computer.
All the locations on the map are currently well within the safe zone. A reading has to go above 100 and stay there awhile before there's cause for concern, according to Radiation Network. Occasionally there are short-term high readings. Sometimes these are caused by a weather system passing over, or radiation on the volunteer, or on the geiger counter. Clouds seem to soak up radiation and if rainwater remains on your geiger counter it can cause extended high readings. Sometimes high readings are caused by radon gas that's not properly ventilated from a crawl space under a house.
The little "Alerts" link at the top of the Radiation Network page opens a page where alerts are logged and discussed. As you can see from the log of the most recent alert, 12/27/13, the site administrator works with the volunteer to try to determine the cause of the high reading, and they begin by trying to rule out false readings.