I think the concern is bin temps might get too warm. I don't know what type of system you have, but you might want to consider putting the current mix to one side and introducing entirely new damp bedding in one area. It won't matter that there's no food. You just want a safe zone for the worms to run to if necessary.

Andrew

I'd be less worried about ammonia and more worried about frying your worms. The best way to get an outdoor compost pile cooking is to add fresh grass clippings. If you wish to add grass clippings to a worm bin, small amounts should be added on top of the bedding, not mixed in throughout the bedding. I repeat, SMALL amounts.

Deanna

Right now it's pretty cool outside. It's been raining. Does the grass act as insulation, or does it just naturally heat up as it decomposes?

It naturally heats up as it decomposes. You can get heat from a compost pile even when it is buried in snow.

Grass is a high nitrogen material, which results in high bacterial activity, which generates heat. It has nothing to do with outdoor temps. Better go check on your worms. They might be goo right now.

Might not be a bad idea to do some research on hot composting methods. Then avoid those methods in a worm bin.

Deanna