I suspect that any loss of ability you have is mainly mental. If you've been climbing long enough that your grade is fairly settled, you're not going to lose much strength in a month. Several yearts worth of finger strength specific gain won't dissapear in a month. What you've probably lost is that subtle familiarity with movement that lets you best apply your strength: the minute awareness of how to weight your feet. I've not climbed for several months at a time and the recovery process was always more a matter of de-clumsification than tendon building.
So, my advice is just to climb - lots of mileage. In this weather going to indoor walls and just spending hours working your way through as many problems as possible. Concentrate on good form whilst doing the easier stuff - careful, silent foot placements - exaggerated grace.
