There are a variety of weather-related lines one can use to start a stimulating conversation with a stranger. This is a form of communication which is often employed by shop assistants and people who have run into old acquaintances and don't have much to talk about.
Popular cliches include, but are not limited to:
In rain:
In sun:
During or before a storm:
- "Looks like there's a storm brewing/coming"
- "It's looking pretty dark out there."
- "It's so humid today... we must be headed for a storm."
While in a shopping centre it's common for conversationally-starved shop assistants to say "Is it still nice/hot/cold/raining outside? I've been in here all day and don't know what's going on". Even as one answers one realises that the shop assistant already knows the answer. They know because they ask everyone who goes in there the same question.
Such is the nature (pun intended) of weather comments. Repetitive and predictable but a social lubricant to keep conversations running smoothly all over the world.