Since in this case you are expressing possibility, then the difference between may and might is very slight. May -> has more chances of happening; higher possibility of happening Might-> the possibility is less than what 'may' expresses. EXAMPLES: I may drop by the office tomorrow because I need to pick up the documents for the presentation. (Highly likely you will drop by) I might drop by the office tomorrow if I need more documents for the presentation. (You'll probably drop by if you need to get materials in the office.) From the examples above, use 'may' if the chances are higher. But please keep in mind, there are many instances that indicate differences between may and might. It is only in expressing possibility that the difference is quite little. Hope my explanation helps. :)

there is no big different but ( may) the Probability of happening is more but might is less ya know like I might have to work late tomorrow evening (40%) will happen and I may have to work late tomorrow evening (70%) will happen