It's a tense time for the boys' families who are waiting for news of their rescue.

For the families of the trapped boys, this is the day they've been waiting for -- but it's also one that fills them with dread.

There's been no shortage of warnings in recent days about how risky the rescue attempt will be -- not least the death of former Thai Navy Sgt. Saman Kunan, an ex-SEAL, who died early Friday morning due to a lack of air while attempting to return to a command center deep underground.

On Sunday, CNN visited the home of Peerapat Sompeangjai, whose family has been glued to the television, waiting for news.

Peerapat turned 16 years old on the day the boys disappeared. During the search, his family said that they hadn't touched his birthday cake, in the hope that he would soon return home to share it.

Peerapat 's 17-year-old sister, Phanphatsa told CNN on Sunday that they'd eaten the cake, but she promised to make him another one -- and all his favorite food.

Phanphatsa Somphiangjai, 17, has been waiting for her little brother to come home. She's promised to make him a new birthday cake.

Outside the house, the rain started falling, a bad sign for families who have been praying for clear skies.

Rescuers have spent days trying to pump water out of cave so the boys don't have to swim against strong currents through narrow tunnels to escape.

Extra rain could make the journey out more challenging.