B757-200
Time Pressure; Communication Breakdown; Workload
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Security; Flight Deck / Cabin / Aircraft Event Other / Unknown
General Flight Cancelled / Delayed
Human Factors; Staffing
Flight Attendants were one hour and nineteen minutes (1:19) late arrival into ZZZ due to weather; snow blizzard; pilot diversion and de-icing.  We landed in ZZZ and deplaning took time. We had a full load of passengers and numerous wheelchairs.  Cockpit crew finished their day and left the aircraft.  Flight Attendants waited for the last passenger to deplane and walked out the Jetway with the Ground Agent. I asked the Agent which gate was Flight ABCC.  Agent responded 'Gate XX'.As I look to the right at Gate XX the agents are in the process of pulling tickets and boarding the aircraft.  The captain was behind the podium pulling his paperwork.  As I approached the gate I thought another flight may have still been on the gate. Then I read the signage at Gate XX; Flight ABCC. I asked the pilot if he was working the Flight ABCC.  He answered 'yes'. I told him we were his cabin crew.  Because of our late arrival time from ZZZ1 did they pull another crew to work to ZZZ3?  The captain gave me the crew list and we were still the original working crew. I asked 'Who is on the aircraft boarding the flight? I stated to the agent 'We are the working crew'. 'Who is on the aircraft boarding the flight'?Agent A looked at Agent B and asked 'Didn't you check the crew?  Who is on board the aircraft'?  Agent A sent Agent B down the Jetway to check if there was a crew on board.  Agent A then checked my ID and the rest of the working crew ID's and we proceeded down the Jetway. We passed Agent B in the Jetway and she confirmed there was 'no crew on board'.  This was a 757 aircraft; we were using the L2 door for boarding.I entered the aircraft there were between 10-15 passengers on board. Approximately six (6) passengers in First Class; the catering representative in the First Class galley wanting to check the galley packing; a non-working uniformed pilot was trying to stow his too-fat for the overhead suitcase in the closet; agent gave an unaccompanied child UNACH to Flight Attendant #4 to sign for and bring on board the aircraft; before the cabin crew had a chance to stow our luggage and check out safety equipment.
A B757 flight attendant crew arrived late for their flight because of weather delays and found that the gate agents had begun boarding their flight without them having had the opportunity to do their pre-flight checks. The aircraft was not ready for boarding.