The second sentence states a fact.
In North America, summer starts in late June.
It can be proved by checking a calendar.
The first sentence states an opinion.
Summers in the United States are too hot.
Too hot shows what a person believes, thinks, or feels. Another person might have a different opinion about how hot is too hot.
Which sentence states a fact?
A: Summers in the United States are too hot.
B: In North America, summer starts in late June.