Good question. I have pondered the same, needing to solarize my raised beds soon. If I water, it should create condensation on the plastic and I've wondered if maybe that would magnify the sun's rays. Still not sure about that, but have read that a deep watering can help germinate those weed seeds, then the clear plastic covering can trap heat to easily fry them. It's the tough, mature grasses like nutsedge I hope it will work on, hopefully getting at the roots they run from.
I need to do some searching on Google and find out if common bean mosaic virus will be killed off by solarization, as I may have found that taking hold in my garden.