IIRC, below freezing also isn't generally good enough -- I forget what the specifics are from when I cared a lot about it 5+ years ago, but it's something like -20C consistently for a few whole days for all the stages of bedbug and their eggs to be destroyed by cold. They're surprisingly resistant to death from cold -- but a good hot dryer at 120F for ~30+ minutes will definitely get 'em.