One of the best features for the traveler is the fabolous Puerto Vallarta weather. From mid October to mid June the temperatures are allways between 20 and 30 degrees celsius without rain fall. During the summer the temperatures go up to 38 or 40 degrees, with one or two hours of summer rain mostly in the afternoon.
The travelers prefer the time between November and May, because they can be sure to have sun more or less all days.
Traditionally november, december and january is the time with the most visits. I prefer the time between march and may, because there are less tourists and the oceans water is well temperatured. Also the hotels prices are lower during this time.
On the provided links in the link area You find some more weather information including some tables and links to other sources.