We to some rain this week. At work I saw new buds on the golden rod, no bees on them yet. I also saw some older blossoms loaded with four kinds of bees as well as wasps and butterflies. The bees I saw were some very tiny halictids, some larger halictids, some honeybees (ligustica) and some very dark bees that looked for all the world like honeybees gathering pollen with full saddlebags. I don't know of any eusocial North American bees; could these have been Buckfast or European black bees?
They had a black spot on the top of their thorax which made them look a little bit like a tiny bumblebee.