A swarm in June is worth a silver spoon. That saying comes from the beekeeping world and refers to the quality of a swarm collected to start a new bee hive.
Basically, a hive collected early in the spring to the first of July can survive very well. The key here is to capture a bee swarm early enough so the new bees can build up their new hive and store enough excess honey to carry it through the winter. Certainly, a swarm in late July or later usually won't make it mainly because the heavy honey flow of spring and early summer is already passed.
If you spot a bee swarm, don't get overly excited because of its assumed danger. Actually, the bees in a bee swarm are very docile and are interested in one thing and one thing only--to find a new location for its surviving queen and find food to consume. The bees in a swarm are docile because before they left the main beehive, they gorged themselves. By the time you see them in a swarm, they are like us after eating a big Thanksgiving meal.
If you do find a bee swarm, it's a great idea to call your local county extension office because they usually have a list, like I do, of beekeepers who would be willing to come out and collect the swarm. Now, if the swarm is located low in a tree or shrub, you can count on someone collecting the swarm. If it's high in the tree or if it's in a dwelling, it is very difficult to collect. If the latter is your situation especially high in a tree, you might wait for a sunny warm day in which case, the swarm will likely find a new home.
Now, if it manages to take up housekeeping in your house, you need to call a pest control company to remove it anyway you can. It can cause some real problems, especially when there is a honey build up in your walls or ceiling. That can be a real mess, so remove a swarm in your house as early as possible.