During a 360° turn on a windy day, the groundspeed of an aircraft will change throughout the turn.
If we start the turn with a headwind, the aircraft will have a slower ground speed and cover less distance.
As we turn through the first 90° this will change to a crosswind, with the aircraft now drifting sideways.
After turning through another 90° the aircraft will have a tailwind, meaning the ground speed is faster and a longer distance is travelled.
Turning through the next 90° we again have a crosswind, causing the aircraft to drift further downwind.
So as you can see, turning with a steady angle of bank on a windy day leads to an oval shaped pattern being flown over the ground with the aircraft drifting further downwind as more turns are completed.
Throughout the turn, the changing ground speed and path over the ground can cause the illusion of uncoordinated flight.
A crosswind pushing the aircraft into the turn can create the illusion of yaw away from the direction of the turn.
A crosswind pushing the aircraft away from the turn can create the illusion of yaw in the direction of the turn.
This can cause the pilot to instinctively want to change the angle of bank. Pilots should be aware of this illusion and be careful to maintain an appropriate bank angle.
It may be desirable for the pilot to choose to alter the bank angle in the turn, for example when orbiting around a particular ground feature (a common request from air traffic control). It is typically safer to reduce the bank angle when flying into a headwind as attempting to excessively increase bank angle with a tailwind will lead to increased load factor and stalling speed.