One of the first questions a therapist might ask is - what happened in the spring time at some point in the past that left a BIG impression? And indeed, Grandfather's death may have something to do with it -but just as likely, his LIFE had something to do with it. What did he mean to you? And, what was going on in your life when he took his leave? The seasons -and certain holiday period such as Christmas are often high anxiety or depression times for many people -even though they are supposed to be "happy" times of year. Go figure.
I have this love/hate relationship with spring too. For one thing it means summer is coming and that is my absolute least favourite time of the year. It''s hot and you can only take so many articles of cloths off to be decent and heat along with humidity brings on alot of anxiety for many people. Back to spring, it is great because it does signify the newness and re-freshening of life but it also is a hectic time for some because it signifies the winding down of some things and the starting up of others. It is a transition time and if you are anything like me, I am not good with change! As JS said, it probably does have something to do with something that happened in our past or in your case your grandfather's passing but to be honest, I haven't got a clue why I feel the way I do about it. I don't mind the spring, but summer has no redeeming qualities at all as far as I'm concerned. Thank God for air-conditioning. In the fall, the allergies hit me again but I don't seem to care as much because I know once the frost hits, I'm golden. I love winter and I don't even know how to ski! If you get cold, you just add another piece of clothing and you warm up. In summer, if it is terribly hot, you can't walk around naked and you can be sure no one would wants me to either. LOL
I am getting to the bottom of my traumatic childhood and ow it has sneaked up to me out of nowhere and is haunting me. Now I have to learn to cope for real! It is really weird that an experience like that would have an effect on us.
I'd like to point out that it has been suggested by many experts that spring is especially bad for people who are prone to depression, anxiety, etc. and that the number of reported cases of depression seem to peak right before or during spring. Maybe your mood has just, or mainly, biological causes.