I would suspect you're in a dearth. Bees get very defensive this time of year if there is no flow and some beast threatens to steal their winter food supply.
Dearth and robbing will do.Did an inspection and about half way through the bees got really aggressive. Swarming around my head trying to sting me all over. Luckily had my gloves on. Was about 4:30 in the afternoon and 85 degrees. What causes this? Wrong time of the day? Wasn't a pleasant experience. Smoke didn't seem to calm them. Thanks, KAD
Have to work fast and be focused.Yes to all the above, and a nod to GregV on the robbing aspect. You are not the only one seen as an attacker - you also expose the hive to robbers who may likely be in the area waiting to jump into an open hive. Then you can get all kinds of frenzied activity going. Happened to me once at this time of year - very distressing. I suggest that you always keep the boxes that you have pulled off during inspection covered rather than sitting open.