We've got a live streamer
Perhaps this week's changes in wind direction are starting to show higher readings after all. I tried to cross check this reading with RDTN, but there's only one source available at this location in the network, and it's reading Bq's in water. The RDTN network displays tons of radiation levels throughout Japan, but half of them haven't been updated over the last three days (at least).
Basically throughout Japan, normal radiation backround levels prior to all reactor hell breaking loose were at or about 0.04 μSv/hr (40 nanoSievert/hr), so if you choose to accept the readings on this stream as accurate, Chiba at 0.3μSv/hr would be reading over 7x higher than historical norm.
Here's my small hang-up with this stream: The camera is zoomed closely on the display with no background visible, and there is no way to confirm its physical location. An unprincipled person out for attention or out to create undue concern could simply place a container of salt substitute or the innards of a smoke detector near the geiger counter to obtain higher readings. It may very well be accurate and i'm not saying it's not, but one thing i've learned about reported radiation numbers official or otherwise - you have to take some of this stuff with a grain of salt.
Edit: The reading on this device just shot up from 0.32 to 0.40 right in front of my eyes (3:06pm Ph time)
Edit 2: Our original source went offline, here's a different source in Chiba