“It can/can’t rain tomorrow,” God said.
“It can rain tomorrow. We’ll be working in the basement the whole day.” (=it could rain tomorrow, but we don’t care)
“Oh, no. It can’t rain tomorrow. The roofers need two more days to fix the leaky flashing at the chimney. (=The weatherman says it’s going to rain tomorrow, but I don’t want any rain before the roof is ready.)
Could it rain tomorrow? O.K.
Can it rain tomorrow??? (you could hear it, but use “could” instead)