。
It might snow in the evening, you know.
Literal
Evening-[at-には] snow [subject-が] fall-might-[sentence-final-よ].
A friendly warning. には here stacks the time-at-に with the topic は, fronting 'in the evening' as the framed context. かもしれない ('might, it's possible that') is the standard possibility modal, and the final よ marks the information as something the speaker is sharing with the listener. A very natural casual weather-talk sentence.