(Beginner beekeeper here, so take all info with a pinch of salt

)
Now is a great time to put swarm traps out. Colonies were building up in April, and the first week of May is going to be warm (16 degrees on Thu/Fri) which means better condition for forage and probably for swarming too. Last year I've caught a swarm using an empty hive on the top of my back garden shed, so now another hive is chancing its luck on the same place. I have already seen bees checking out the hive three weeks ago, but they were just robbing some leftover honey from the used comb in the hive. Still, it means that some bee colony is near and if they do decide to swarm, they may remember the path

The advantage of the trap over gathering a swarm is that if the bees arrived into the trap, they mean to stay there. Whereas a swarm on a tree branch somewhere still have not picked the place to go, and when you put the swarm into a hive, they may decide to leave for what they think is more suitable place.