The suspense in this statement from Romeo and Juliet arises from the fact that it is foreshadowing the fight to come betweenTybalt and Mercutio, whose death at Tybalt's hands sets the stage for Romeo's eventual undoing and the deaths of the two lovers. . The feud between the Montagues and the Capulets affects everyone connected to them; tempers are hot; insults are quickly answered with the sword; and Benvolio knows that Mercutio is hot-headed and always ready for a fight. He is making a futile attempt to get them out of public space before a "brawl" with the Capulets becomes inevitable, as it does.
The above answer is absolutely correct. The day is hot, meaning tempers are short. Benvoilio knows that if they encounter the Capulets there will be trouble.
As we, the audience, know Tybalt is looking for a fight. He had to be restrained by his uncle at the masked ball.
It is a hot summer's day. The youth are bored. What better way to pass an afternoon than to verbally taunt your enemy? But, boys will be boys, and when manhood is on the line, anything can and does happen. Does Tybalt mean to kill Mercutio? It is a tragic accident but the result is tragic for both families and the city of Verona itself.
A tragedy is like throwing a pebble into a pool of water. Once thrown, we cannot control the ripples that spread out from the center. The results are beyond human control.