If you want a good idea of what kind of radiation is blowing into Northern California from the nuclear power plant meltdown in Japan caused by the recent earthquake and tsunami, you can go to the UC Berkeley Department of Nuclear Engineering website for your daily update on what kind of dose you’re getting. They are also monitoring rainwater. Click on the source below and it will take you there.
If you go to their Frequently Asked Questions page there are links to two other monitors and other important information such as the half-life of various isotopes.
Source: UC Berkeley Nuclear