hawaii accomodation

I will be heading to Big Island in Hawaii in the first week of June. Does anyone know if I will need to pre-book accomodation, or if it should be easy to get just when I show up? I'm looking for budget hotels and will be going from Hilo to Kona.

Any advice much appreciated!

You are in the wrong forum here, Hawaii is in the USA branch.
There should not be a problem with getting accommodation in either Hilo or Kona on arrival.
Make sure you go and see the lava, hopefully it will be flowing and is a great sight at night at the end of Chain Of Craters road.