If you look at the precipitation graphs for
Kota Kinabalu
on the west coast and
Sandakan
on the east coast, they're very different, considering the two cities are only about 130 miles apart, but both actually show more rain in September than in May. I thought it would be the other way round too!
Have you looked at any other operators? The one we're going with does holidays all year round and you can either choose from a set tour or tailor-make your own holiday from a choice of different modules.
Elaine