Technically, it already happened (is happening).

Last Friday was said to be the worst day. It disrupted cell phones and things like that. Also, many northern states could see the Northern Lights that normally can't. (It was too cloudy in MI that day )

There was a Solar Flare yesterday also, but it won't reach Earth till sometime today.

Tuesday's Solar Flare Largest Ever Seen

Yes there will be a slight increase in radiation so if you're in a very sunny location, wear sunscreen, but the worst these flares do is disrupt cell phones, sattelites and the such.