Its also a normal time of year for bison to migrate... people are making a huge deal out of this anyways.
If the yellowstone caldera does blow up, pretty much anywhere within a 500-1000 mile radius is going to be instantly fucked, so I'm not too worried about it.
The yellowstone caldera is also "due to blow up any day" and has been for years, so yes it could blow up, but like jake said, if it blows up you will definitely know. No one knew Mt St Hellen was gonna blow up, just one day it exploded, thats how volcanos/calderas work.