Might and could are often confused, and the difference between them is that "might" refers to an event that is a real possibility, whereas "could" refers to an event that the subject is able to do. "I might go to the supermarket today", I am seriously considering going to the supermarket. "I could go to the supermarket today", it's a possibility, but I'm not giving it a lot of consideration.

"Could" is the simple past tense form of "can." "Might" is the simple past tense form of "may." These past tense forms are commonly used with the subjunctive mood, expressing doubt, hopes, or hypotheticals. For example: "I wish I could speak Spanish better." "If I get my homework done I might go out tonight." In the past tense form: "She could speak Spanish."Yesterday my papa said that it might rain today."