I have a road trip through the Yucatan and Quintana Roo (including a whale shark swimming session on Isla Mujeres on Saturday 5/12) but the current weather forecast is projecting scattered thunderstorms or rain everyday for the next week! Does this week seem like the usual coastal rain where it rains half an hour and the rest of the day is beautiful or does this seem more like a nonstop stormy week?

Wondering if we should postpone our trip! The next time we could go is August, which is approaching hurricane season. Does anyone have advice for us? Thank you so much in advance!

I'm not a local, but have been to the Yucatan many times. I have found the weather forecasts to sound much more dire than what really happens. You will typically brief showers, rarely all day rain.

I don't think there is any one on this board who lives in the Yucatan.

Don't think whale shark season is open May 12, might want to double check that your tour is not being done by an unlicensed operator.
Whale Sharks Tours on Isla Mujeres Mexico - Frequently Asked Questions

Hey, I'm a french expat in Mexico, and weather forecast is always a good question.
As some other said, you might face some rain but it is never for a whole day. August is a good season to travel in Yucatán and Quintana Roo but it is considered as "peak seasons" because of european holidays.
I'm pretty sure you'll enjoy your stay, even with a few rainy days =)