What to do during the rainy season? (Managua)

My husband and I are planning our move to Nicaragua so we have been exploring different areas (we've been there last September and then again in January/February). In two weeks we are returning to Nicaragua and planning to spend most of our time in Leon, Poneloya, and Las Penitas (though we're very flexible and can change that). My question is, what is there to do in the rainy season? We were there in September last year and it only rained at night...from what I've seen, it rains pretty much all the time at this time of year? We also plan to spend about 24 hours in Managua. Any input would be very much appreciated!