To bank on something is to rely on it happening. Do not bank on it, bank on the weather holding.
It is used most in the negative, as a warning not to. It means depending on something you do not control, which is what makes it risky.
1phrasebank onTo rely on something happening.
“I would not bank on the train being on time.”
bank on is a phrase.
Practised in Phrasal Verbs