What are examples of foreshadowing in Act 2 of Shakespeare's Romeo and Juliet?
One good instance of foreshadowing can be found in the famous balcony scene. Juliet feels that exchanging vows of love "is too rash, to unadvis'd, too sudden" (II.ii.124). In other words, she believes that they are acting foolishly. She couples her opinion with a simile declaring that vows of love are "[t]oo like the lightning, which doth cease to be / Ere one can say 'it lightens' (II.ii.125). This simile serves to compare love to a passionate fire, like lightening, that flares up and dies suddenly. Since this simile refers to an image of death, specifically death of lightening, it can be seen as foreshadowing the couple's upcoming deaths.
A second instance of foreshadowing can also be seen in this scene when Juliet speaks directly of death. Juliet says she wishes Romeo was her pet bird so that she can keep him trapped near her all the time. When Romeo replies, "I would I were thy bird," Juliet warns that if he were, should would be likely to "kill [him] with [too] much cherishing," meaning hugging, petting, and kissing until the bird suffocated. This metaphorical reference to killing Romeo with love as a pet bird can easily be seen as foreshadowing Romeo's upcoming death.
There is a good example of dramatic foreboding (foreshadowing unpleasant events) on the last line of scene 3.
"Wisely, and slow. They stumble that run fast" (2.3.97)
This is said by Friar Laurence after talking to Romeo. He is warning him about being so quick. It is this haste that later on in the play results in Romeo and Juliet's death and his line dramatically forbeodes it. It is due to the increased speed of the loveres weddng, Juliet's father wishing her to marry so suddenly and Romeo's anxiousness to die and be with his love; that end with their death.
*if you did not understand what it in bracets, the order it Act, Scene and line
I hope this helps