We have had a lot of rain the last month in Los Angeles and the weather has gone into the 40′s many nights.   If you have not looked in your hives since this change in the weather, please have a look to see if water is condensing on the underside of the top board. Because of the cold outside air and the warmth and moisture of the bees and their evaporating nectar inside the hive, there is a tendency for moisture to condense and drip down upon the bees. This is very unhealthy for them!   The water condensation is likely to happen even with the inner cover/outer cover arrangement, too.   I do not find that hole in the inner cover is enough to allow thorough airflow.   All my bottom boards have 4 vent holes, 2 inches in diameter, covered with screening cloth, but more venting is still needed in winter weather.   

I checked all my hives two days ago and found water accumulation, and  some lids with black mold growing. Only one hive, which had retained a shim under the inner cover from placement in the summer, was dry. So, whether you are using a telescoping cover with a inner cover or a migratory cover, ventilation of the warm, moist air must be accommodated. After wiping the water off the lid underside with a old towel, I placed small chunks of wood  under the covers to prop them up. These I picked up off the ground from the abundant mulch, but you could use anything that would allow airflow.

Some beekeepers make a small shim, called a Imrie shim, to place under the inner cover or migratory cover. This would work well, too.   But, the first step is to do the checking, so please be sure to get out there!