I have to disagree with summer being the best time of year for tickling. Among other reasons, summer is hot and, in some regions, quite humid (it sure is around here). While in some cases it might actually help, serving a purpose similar to lotion, my personal experience is that in most cases, getting hot and sticky usually decreases ticklishness, especially on the feet. In particular, light techniques like using a feather or gentle fingers just don't cut it with sweaty feet. Even more vigorous methods can see their effectiveness lessened, with fingers tending to slip on the skin instead of really digging in. You can't scratch as well, you know. No traction. Besides, not everyone likes to mess around with other people's ticklish areas when they're covered in sweat. My experience indicates thay dry skin tends to be significantly more ticklish, and, in my opinion, more pleasant to work on. Reasonably warm (but not hot) and dry skin is best.
Another problem with the summer heat is that a ticklee can get tired much quicker if it's hot and humid enough. I've actually had to postpone a number of auditions because the weather was just too oppressive. It would have been unpleasant, and chances are that candidates that are otherwise rather ticklish would have performed poorly during the audition because of the heat (not to mention a full commercial shoot). In fact, I'm pretty sure I must have turned down a few candidates with good potential in the past because the heat ruined their audition. A shame.
Besides the technical reasons, my personal preference is when models are fully dressed. For instance, I really like the contrast between covered legs and the bare feet that stick out of the pants or jeans. Kind of like the ankles are trapped or something, you know. There's also the mystery factor, when the ticklish areas are covered at first. Typical summer light clothes don't leave much to the imagination. I prefer to have to work to get to the ticklish parts. Tickling already bare skin is too obvious, too easy. Just my opinion, you understand.
I also like the footwear-removal process: the shoes being unlaced and thrown aside, the socks being slowly peeled off, etc. It's not the same when the ticklee is already barefoot or barefoot in her shoes or sandals. Again, the mystery factor. And the tease factor too.
I was a much more active tickler when I was a young teen, having more friends and friends' sisters with whom to have fun. Of course, at that age it was also easier to get away with such behavior. One of the things I really liked was when I had to struggle with my "victim", holding her ankles still and peeling off her socks while she laughed her ass off while playfully begging me to leave her feet alone and trying her best to keep her socks on her feet. It was great when the socks finally came off and I could start digging in. I don't get to do that anymore, and to be honest I kind of prefer when the ticklee is restrained in some way so that she can't really fight it (like in my videos), but fighting to bare those hidden feet was a real thrill back then. Very few opportunities like that during the summer.
I must admit that in my case, easy access to ticklish areas isn't a factor. The only times I get to do tickling is within the context of my video project, and when I shoot a video the models are supposed to get tickled, so they wear whatever clothes are necessary and they lift or pull them off to reveal ticklish spot as needed. They don't need to have body parts already exposed for me to get to tickle them (or, as happens much more often, for others models to tickle them, sinme I usually don't contribute much to the action itsef).
Of course, for other people who tend to take advantage of tickling opportunities in everyday life more often than I do, people who have acceptable tickling victims (like friends), I can see how bare skin in summer can be advantageous. It's just that I don't get such opportunities myself. I can't picture myself tickling anyone like that when not doing a shoot. I don't have relationships that allow it. So summer isn't especially useful for me.
So anyway, assuming that a tickling opportunity takes place indoors, I'd have to say that, for me, any season other than summer is best. Winter is just fine by me. But again, my project allows me to have the models get barefoot, wear armpit-revealing tops and have their shirts lifted to uncover the bellies, no matter what the season. And I really don't find myself in situations that allow me to tickle people on the spot (in which case I admit light clothes and bare feet could indeed be useful at times), so my case is not quite the same as for other people.
Francois A 
