This is usually the best time of year to visit Mexico's Monarch butterfly reserves, but unfortunately, flooding and landslides in eastern Michoacan state have made it impossible to visit the reserves there, at least for the time being.
The town of Angangueo, located very close to Michoacan's Monarch butterfly reserves, has been devastated by landslides caused by very heavy out-of-season rains, which have destroyed property and roads, and caused several deaths. The Mexican government has declared Angangueo and surrounding areas a disaster zone and the area's inhabitants have been evacuated. There is also the possibility of more rain, which could compound the situation.
The monarch population was already at an all-time low, even prior to the flooding, so the prospects for the butterflies are looking grim, though the full extent of the damage has yet to be assessed. If you're still planning to visit the Monarch butterfly reserves this year, your best bet is to visit the ones that are located in Mexico state (Estado de Mexico).
More about the Monarch butterfly in Mexico:


Is it still the case that trails to see the Monarchs in Santa Rosario Monarch sanctuary are not passable?
Hi Nan,
Apparently some sections of the reserve are closed off, but it is possible to access the reserve now. You can read a recent trip report to the butterfly reserves, and information about the damage caused by the storms here: Driving through Mexico after the storms, from Monarch Watch.