Tonga in August - should I be worried about El Nino?

Hi,
I am looking to go whale swimming in Tonga this August in Ha'apai. I was just wondering, how much of a worry is El Nino to this area. I have read that there is one forming in the Pacific and what effects might this have on tourism in this part? I know it pisses down rain in South American usually around Jan/Feb usually while causing droughts in Australia, but what about these islands?
Thanks!