The question is testing our understanding of modal verbs and their appropriate usage in context. Modal verbs are auxiliary verbs that indicate likelihood, ability, permission, or obligation. Let's examine each option:

1. Option: "can"
   Explanation: "Can" is a modal verb used to indicate ability or possibility. In this context, it suggests that it is possible or likely for the summers to be really hot. This fits well with the sentence as it conveys a direct possibility.
2. Option: "could"
   Explanation: "Could" is used to express a conditional possibility or a past ability. While it can indicate possibility, in this context, "could" often implies a more hypothetical situation or past possibility, which does not fit as well when stating a general fact about summers.
3. Option: "might"
   Explanation: "Might" is used to suggest a smaller possibility or a less certain situation. Although it indicates possibility, it carries a sense of uncertainty, which is not as strong as "can" in expressing the likelihood of summers being hot.
4. Option: "may"
   Explanation: "May" is used to express permission or a smaller possibility than "can". While it can also suggest potential, in common usage, "can" more strongly conveys the factual likelihood that summers are generally hot.

Conclusion: The correct option is "can". It best aligns with the sentence's intent to express a factual and likely situation regarding summer temperatures. The statement implies that it is generally possible for summers to be really hot.