Took the partial transit (Gatun Locks) in early November ... no problem with weather in the Canal area. Took the boat excursion in the rain forest in Limon ... and it rained, but what do you expect for a rain forest!!! <G>
I cruise the Emerald Princess, Eastern Caribbean on April 16, 2012
I can only answer to my own experience, late Nov. 2000 on Celebrity Mercury. Our crossing was clear and sunny and hotter than anything I could even begin to imagine.
We crossed from Pacific to Atlantic. Wear a hat, tons of sunscreen and drink plenty of fluids.
I got up at 445am and got the dead center railing on the upper deck for viewing.
We stayed upstairs through the first set of locks, and until we entered the second set, then relinquished our prime seats to someone else and experienced the second set through a window seat in the dining room. We sat on the covered promenade deck
for the transit of the cut and lake (I scooted back and forth a bit for pictures). We watched
the ship enter the Atlantic side locks from the promenade deck , then watched the ship go down from the stern decks with a 900 foot cargo ship adjacent and above (behind us)in the opposite lock. Caught a late lunch in the dining room as we sailed out to sea.
I hope you enjoy yor experience as much as I enjoyed mine.