Hi Richardus,
don't worry. I've been on Tobago in almost every month of the year, rainy season or dry season. Normaly it is raining. Less in the dry time and a bit more in the rainy season what is from April to October/November I guess.
I had dry days in June and rainy days in January but normally it rains not more than one houre or less. If you are lucky it rains in the night. The rain is washing the dust away and it is humid for a while but the wind will blow it away soon.
Anyway. You booked your trip and will not be able to change the waether. Just take it as it comes.
I'm sure you will have a great time
Gary and Helen, I relaly envy you! Have a Carib on me!
Cheers
Gisela