At the beginning of the scene, why does benvolio think that there will be a fight?

The feud between the Capulet and Montague is deep. to show this Shakespeare puts this fight in the play. Benvolio knows theirs going to be a fight because the tension is huge and the fudge is just to strong. i may be wrong but i had the same question and said this and got is right but who knows.

It's hot outside, tempers are too, and the Capulets are out as well as the Montagues.