Should the rains further flood the cave, as predicted, the team could be trapped in the cave for more than four months until waters recede.
Provincial Governor Narongsak Osotthanakorn said the mission was a 'race against the water.'
'Our biggest concern is the weather. We are calculating how much time we have if it rains, how many hours and days,' he said.
The boys, who range in age from 11 to 15, as well as the coach, have practiced wearing diving masks and Thai Navy SEALS are being told to prepare for a sudden evacuation.
The boys are reportedly still too weak to attempt to leave the cave, with two boys and the coach suffering from exhaustion.
After a day of exploring in the Tham Luang Nang Non cave in the northern province the boys and their coach became trapped on June 23. Monsoon flooding cut off their escape and prevented rescuers from finding them for 10 days. The boys, although skinny, have been described as in good health. Authorities have said the soccer players are being looked after by Thai navy SEALs, including medics, staying with them inside the cave.