1994 Pontiac Sunbird Electrical problem

My car has having issues with the electrical system which seems very confusing. Last winter it began when the horn would randomly tap on and off very quickly. It did this a few times but as the weather got warmer there wasn't a problem. Now that the winter is back, it has gotten worse. The horn did this until I disconnected it and now the rearlights and blinker lights will flicker on and off. There is also a clicking sound coming from the left of the steering wheel (near the fuses). This morning my dad started the car and the starter would not turn off until we disconnected the battery. I went out at lunch to try it again and the starter worked fine. It is just really confusing that it will happen when the weather is extremely cold. I hope you can help me. Thanks.