Jay: I can’t believe mom bought us a trip to Hawaii. Maybe she’ll get us a car too.
Saul: Calm down Jay. One swallow does not make a summer. Remember that mom has money limitations. Let’s not get ahead of ourselves.
Jay: You don’t think mom would do that for us?
Saul: Be realistic. Just because mom got a new job, doesn’t mean she can afford everything.
Peter: I got into college in NY. I’m not worried anymore. I’m sure all the other colleges will accept me too.
Sonia: One swallow does not make a summer buddy. Every school has different standards and rules. Let’s not get too confident about what schools will accept you yet. You should wait before making a decision.
Peter: But this was the most difficult school to get into. How can the other schools not accept me?
Sonia: Sometimes school departments make a difference. It’s not necessarily the entire university that makes that decision.
Meaning: The expression "one swallow does not make a summer" means that just because one good thing happened, you cannot expect every other thing that will happen to be good. For example, some people think that if something good happens at the beginning of a trip, it’s a sign that everything else will go well. In reality, that is not true. In the first example, Jay thinks that because the mother bought them a trip, surely she will also buy them a car, but there’s no evidence to prove this. It’s just a feeling. In the second example, Peter thinks every college he applied to will accept him because he got into the most difficult one. However, that’s just his belief, not a fact. He is not aware that most universities have differences in acceptance policies and that the standards of each department in that college vary.