The weather forecast says that the probability of rain in a city tomorrow is 95%, which means (a) the rainfall in this city tomorrow is 95% of today's rainfall; It will rain in this city tomorrow.

A, the probability of rain tomorrow is 95%, and it is not said that it will rain tomorrow, so this option is wrong;

B, the probability of rain tomorrow is 95%, indicating that it is likely to rain in the city tomorrow, so this option is correct;

C, the probability of rain tomorrow is 95%, and it is not said that it will rain tomorrow, so this option is wrong;

D, the probability of rain is 95%, 95% means more possibility, so this option is wrong.

So choose B.