When to add boxes?

[MoKen]

I'm a newbie needing guidance.

I just got my package about a week ago. Installed them in one medium. They immediately filled up 6 frames with some spillover. Despite the cool, wet weather, they have been collecting pollen and consuming syrup.

It looks like good weather in a couple of days so I plan to open the hive up for a good look. What are the indicators that it's time to add another box? With the cool weather I don't want to give them too much space to keep warm, but I also don't want to crowd them. I know the population is decreasing just now until new brood can hatch. Is that a factor? Should I wait until there are new bees?

Also, I have the entrance reducer on the smallest opening. On sunny afternoons, there is a lot of activity around that opening. Should I temporarily switch it to a bigger opening or just leave it until the weather is definately warmer?

Thanks in advance. This is a great forum.

Ken

[Horns Pure Honey]

Add your second brood box when they get 80% of  the frames filled out. bye :D