There isn't a lot of information out yet for early 2016 in terms of events and activities that may be happening in and around the parks that will impact crowds. I've finally gotten the
2016 Calendar of Events thread up, but it's still pretty sparse. You can check out the
2015 Calendar of Events thread to get a sense of the types of events and activities that happened this year during Jan-Mar and May.
HydroGuy has a thread that details the
weather. He also has a thread with links to the
historical calendars (as compiled in the wdwinfo archive), which includes operating hours, refurbishments, etc. Note that the operating hours for DLR tend to be posted 45-days/6-weeks in advance. Refubs, entertainment, etc. may not be added until much closer to the date.
In general, DLR does not really follow a set refurbishment calendar. Splash and Grizzly Rapids usually go down at some point in the winter. HM and IaSW usually go down in January to have their holiday overlays removed (HM usually goes down first, then IaSW closes when HM re-opens), but the dates can vary from year-to-year.
Usually, fireworks, F!, and Mad T Party are only presented on weekends and holidays during the non-peak season, and WoC is usually presented nightly. It's worth noting that things might be a little different in early 2016 - we don't yet know what the schedule will be. DLR is presenting fireworks and PtN nightly during HalloweenTime this year, which is unusual. So it's possible that fireworks and PtN will be nightly throughout the 60th Celebration or they may go back to the weekends-only schedule next year - we just don't know yet.
May tends to be a variable month, depending on when you're going. Memorial Day Friday has been the kick-off to the summer season lately, so it means that pre-Memorial Day crowds tend to be lighter, but operating hours and entertainment are reduced. Starting with Memorial Day Friday, the parks transition to longer hours and more entertainment (e.g., daily fireworks, parades, F!, and WoC), but also bigger crowds. For the last few years, the 24-hour day has been on Memorial Day Friday, so expect high(ish) crowds then.