Why are the Jellyfish Here Early?

After NYC Triathlon competitors complained of jellyfish in the Hudson Rivers, attention is now on why the marine animals have appeared about a month early. The NY Times says one theory is "recent winds from the south that blew away the sea’s warmer surface water, allowing an upwelling of cold water," creating a perfect environment for the lion's mane breed of jellyfish. And marine biologist tells the Sun the Sea Nettle breed's stings can "really hurt." But the sting aren't considered dangerous, unless someone has an allergy.