|Subject: Re: Mexico, the colonial cities.|
As you may have noticed by following the historical weather links that Linda provided the average temperature for both Guanajuato and Querétaro will be moving up into the 60ºF+ range at the time you'll be visiting. These cooler temperatures (compared to Puerto Vallarta and the rest of the coast) are due to the higher elevations and not because cold fronts from Canada are sneaking across the U.S. and into central Mexico (extremely rare for this far south in Mexico). All you need to remain comfortable is to pack a sweater. You'll be visiting during the dry season so rain shouldn't be a problem.
John in San Diego