This is common…Tire pressure drops 1lb per 10 degree drop in temps.
Here’s one other bad thing about nitrogen…If you want to stay with 100% nitrogen you can’t just use a standard air pump at the gas station.
You really should NOT rely on the tire pressure light to tell you when the tire pressure is low…Get a gauge and check it periodically.
BTW…the converse is also true…when temperatures increase so does tire pressure.