I am in central Alberta, Canada, Zone 3. I just moved into a house that has raised planting beds for a veggie garden but is COMPLETELY full of crab grass and various other lovely weeds and grasses. It is too late this season for a garden anyway, but want to have it ready for next year. Not sure if solarization would work here - it gets lots of sun and is hot right now, but generally cools off by end of August. I don't want to use chemicals since I will be growing food I will eat. thanks!
I would pull, cut, or somehow trim the grass/weeds to a low level, then pile on a THICK layer of FRESH grass clippings and cover the clippings with soil. With this method, I can stop even most persistent bermuda grass, while at the same time fertilizing my soil with the protein and nitrogen rich grasses. Next year at planting time the soil will be extremely rich and loose.
You could also just lay a tarp or similar covering to hide the sunlight from the weeds. This doesn't add much to the soil, but its easy.
Another option is putting newspaper over the weeds (at least a few sheets), then cover the paper with grass clippings. Cardboard will work too. The newspaper and cardboard won't add much to the soil either, since they're cellulose (C6 H10 O5), they mainly break down to CO2 and water. The plus side is newspaper and cardboard are free.
Crabgrass is an annual weed. It will die off on it's own when it gets cold. Unfortunately it will come back next year.
I would give solarization a shot for at least 6 weeks so you can kill any of the seeds to prevent them from coming up again next year. Chop or pull everything first so you don't have a lot of air under the plastic. On my blog, I describe my results with some organic weed killers. They worked well for me.
The UC Davis guide on solarization is one of the best I've read. If it gets too cold before you're done solarizing the soil I would do it again in early spring too. I'd probably do it again anyway just to kill off some more pathogens.