Usage patterns
昼になるfor it to become noon
While we were talking, it became noon already.
昼から〈動詞〉to do something from noon/daytime onward
It started raining from noon onward.
昼を食べに行くto go get lunch (casual way of saying 昼ご飯を食べに行く)
Expressions
昼の部daytime; noon period; matinee