I originally intended to visit Tikal on Sunday, giving it 1 day for the rain to pass and hopefully better weather.
However the staff at RETPSA that sold the ticket said it would be better to do it on Saturday, as admission is free for locals on Sundays, and Tikal would be crowded. They also mentioned, that the rain usually starts in the afternoon, and so I signed up for the 4.30am trip departure on Saturday.
It poured heavily before I left the hostel in the wee hours of the mourning, and stopped momentarily as we walked towards the shuttle and started again on the 1.5hr drive towards Tikal.
Fortunately, throughout the entire time we were on our Tikal tour, there wasn't any rain, and interestingly enough, the moment we hopped onto the shuttle to head back to our hostel, it started raining again.
Someone must be looking out for me, as I also had fantastic weather on my snorkel trip in Caye Caulker, in between a couple days of downpour!