You'll find that cancellation come and go in stages. I've had 7 on the trot cancelled, yet once during training managed nearly 30 hours in 4 months without a single one. Get the lessons booked up months in advance, never mind weeks! I'm sure any decent school will let you cancel with a day or so's notice if you find you're flying too much or just can't make a lesson.
My formula was to book 3 slots a week (Mon, Wed and Sat) and plan on flying twice if I was lucky. That way you're never more than a couple of days from a possible lesson and shouldn't miss out on any good spells of weather which might materialise.
One thing I'd recommend later on in your training, is to fly in marginal weather as much as your instructor thinks is safe. I learnt more from 60 minutes of 'poor weather' low level circuits in crap viz. than I did in 4 or 5 hours in 'perfect' weather. If the weather's poor and you have to stop after 15 minutes, so what? The time's still loggable, and you've leart a valuable lesson.