In reply to Ula S.:
Depends where you're based. If it's southern England as above. Brean, some bits Cheddar (Easter Island, Sunnyside terrace - other areas can be Siberian), Cuttings at Portland, and the Swanage quarries can all be good. All S to W facing.
Pay close attention to the weather forecast: air temperature is rarely the limiting factor, direct sun is critical, and the wind direction should be blowing over the top of the crag not towards it or along it.