does anyone know when swarming begins in northeast pennsylvania
Are you seeing something that makes you think your hive is going to swarm or has already swarmed? Reproductive swarms are most likely in the Spring. If your hive is overcrowded, it can swarm anytime.
Before your hive swarms, the bees will make queen cells. The swarm will leave about the time the queen cells are capped.
http://www.bushfarms.com/beesswarmcontrol.htm (http://www.bushfarms.com/beesswarmcontrol.htm)
Swarming in that area probably is greatest from Late April through mid June. You can also have a lower swarm rate later than this depending upon nectar flow.
Swarming is closely related to flows. No flow, you have almost no swarming. Simply put, most insects will perpetuate their species in times of plenty.
Many beekeepers take honey off at the end of June when the main flow stops. In doing so, it is normal to compress the bees down to a lower number boxes. Of course you have bearding, and congested boxes. And after you remove the supers, the bees are forced to pack in nectar down below in the brood chamber, many times limiting the queens room for egg laying. Which depending upon the type of queen, is a good thing as she will be shutting down in a dearth anyways. So why don't we see a huge spike in swarming in July? The answer is simply due to a lack of flow.
We will have a secondary swarm season in September, with as much as 20% of the yearly swarming at this time. Why so late? The answer is based upon the fall flow of aster and goldenrod. In areas of aster and goldenrod, and even in areas in Florida with Brazilian peppers, bees will swarm if there is a flow. And in areas with no fall flow, no swarming spike will be seen.
Yes, regardless of what we do, swarming will happen. And you can lower the swarming urge by keeping young queens, placing extra boxes on, etc. But as many have seen with packages and first year queens, bees will swarm sometime before they even have the first deep drawn during main flows.
Way too much emphasis is placed on "congestion". Swarming is mostly tied to the ingrained nature of perpetuating the species, and doing so at optimal times such as during flows. Understand the flows in your area, and you will also understand swarming.