Hi Sam
The weather forecasts always seem to predict rain because it is very common for there to be a shower at some point in the day or night.
The showers rarely last more than 20 minutes and occasionally you could have a very showery day ... I have said previously that the very worst you could expect on a 2 week holiday is about 2 days of rain ... I emphasise that as the worst.
As Steve says, the weather has been unusually hot and dry recently but there is rain around the southern Caribbean ... Tobago has not had it's fair share though.
Whatever happens, I am sure you will get plenty of sunshine
Regards