What does it feel like to be a widow after 40 years of marriage?

I’ve been struggling with the wording of this question and I still don’t know how to ask it.

My mother passed away December 30th of last year, just a few weeks after her 45th wedding anniversary. My father survives and lives alone now. I’m the only relative who contacts him more than once a week. He’ll be 80 in February.

Do you know anyone who lost a spouse after decades of marriage? How did they cope? How much contact with relatives did they need after their loss?

I worry about my father living alone during a harsh winter. I can only imagine the loneliness that he feels. Any words of encouragement or experience that will help me and my father during this difficult time?