![\huge{\boxed{\text{January}}}](https://img.qammunity.org/2020/formulas/mathematics/high-school/rgzb74iz1943c2jcqqwtgv8s6ozoxg021n.png)
A counterexample is an example that proves the statement wrong.
In this case, we are trying to prove that not all months that start with J are summer months. This means we need to find a month that starts with J that is also not a summer month.
is the only month that fits this criteria. It begins with the letter J and is a winter month, which is not summer.