One of the earliest signs of swarming is an increase in the drone population. You may see this before you see swarm cells.

The easiest and surest way to know if your hive is ready to swarm is if you see ripe or capped swarm cells. These will be hanging along the bottom bars of the hive frames. There is a quick way to check for swarm cells. Tip your hive boxes up on one end so you can blow some smoke along the bottoms of the frames. Look for peanut shaped cells hanging down. This way you do not have to remove every frame to look for swarm cells.

Another sign that your hive might be preparing to swarm is if there are a lot of worker bees gathered at the entrance. They will not be foraging (collecting nectar and pollen).  This can sometimes look like a large beard of bees hanging from the entrance, and the base. If you see this during the heat of the day, it may just be because of the heat. If the beard of bees stays into the evening you should expect that a swarm will soon happen.

Something else you may notice is that the queen will slow down and stop her egg laying before she leaves the hive.  So if you see swarm cells and don’t see eggs you can be pretty sure that swarming is about to happen.