I've definitely been in the situation of having to scramble for clothes to fill gaps or alleviate boredom, so a part of me says, "shop early/now!"
Aside from the usual climate-related stuff, though, I've also been in the situation where I didn't know:
* what my lifestyle/job requirements were going to be (buy for current situation, or try to anticipate what would be useful?)
* if/when my clothing budget was going to replenish itself (save/wait then spend, or spend in wee drabs if possible?)
** if/when some weight changes were going to reverse themselves (buy current size and alter or donate later, or hold off?)
Sometimes all three things were going on at once...fun times!
If everything is as stable as it can be, then I find it's easier to buy what tickles my fancy early on.
Now is about the time I TRY to start pulling stuff out of the closet that is remotely spring/summer appropriate (I have lots of trans-season stuff) so I can get an idea of what already works together, what gaps I have, and what colors might best integrate with existing items.
SO boring (IMO!) but useful.
After doing this last winter I was able to nab some short-sleeved Ts etc in March that sold out a few months later; mine didn't see full daylight til June -- and I was glad to have them then! This year that technique is helping me justify a few impulse buys that I'm actually able to layer up now, but will work with the most warm-weather-y of my clothes.
Let us know how it goes for you!