The local surroundings also has something to do with it. Where the OP indicated he was in New York, it would not surprise me if the taller buildings down there are affecting the signal.
The construction of the building can also affect signals as well. If you are inside a building made of steel, that will also have an effect on the signal. You could have no signal inside such a building, but as soon as you move to a window, the signal returns.
America Movil/Straight Talk/TracFone customer since 2004.