1. You can, but it could be more difficult.  When it’s really hot, the limewash could dries very quickly, limiting the working time to remove the product for distressing and/or erasing it.  When it’s cold, dry times increase and the job takes a lot longer.  The best days for limewash are actually those warm, overcast days where you typically wouldn’t paint outside. It’s a little different than regular exterior paint weather since moisture isn’t as much of an issue.  We actually have to wet the house down to allow the lime wash/masonry flat to absorb and we often use water to distress/achieve the look, so water is a natural part of the process