そうです: reports and appearances
降るそうです and 降りそうです differ by one character but rely on different evidence. Distinguish relaying information from making a judgment based on current signs.
Relay reported information
天気予報によると、明日は雨が降るそうです。 means 'According to the forecast, it is going to rain tomorrow.' そうです follows the plain form 降る to relay reported information.
Nouns and な-adjectives include だ: 休みだそうです and 便利だそうです. Past content retains its tense, as in 降ったそうです. Naming the source makes the basis of the report clearer.
Judge from current signs
Looking at the sky and saying 雨が降りそうです means 'It looks like it is going to rain.' Remove ます from 降ります and add そうです. This differs from relaying a forecast with 降るそうです.
おいしそうです judges something to look appetizing; おいしいそうです reports that it is said to be delicious. The presence or absence of the い helps distinguish the source of the information.
Special forms and limits
For appearance, いい becomes よさそうです. Do not simply remove い to produce いそうです. When modifying a noun, use そうな, as in 楽しそうな人 (a person who looks happy).
Saying something looks appetizing is not evidence that you have tasted it. Reporting that rain is forecast does not mean you personally inspected the sky. Practice explaining both the form and the source of information.
Check: Which relays reported information: 雨が降るそうです or 雨が降りそうです?
Show the answer and why
雨が降るそうです relays information. 雨が降りそうです expresses a judgment that rain seems likely based on current signs or circumstances.