Boston has very defined Seasons, and all are great to experience.
Winter is cold and sometimes harsh. To live and work in the snow and cold is brutal. in December the sun goes down at about 4 pm, and that makes for some depressed people (millions of them) However, play time in the winter can be great fun. That first snowfall is a sight to see, snow covered pines, blankets of white snow.
Spring: ok, The winter is long, by the end of March things begin to warm a bit and you think Spring is here, you begin to relax a bit. Trust me, Winter is not over. Just when you begin to cheer up, one last freak storm comes to town. But then one day you wake up, all the snow is melted and trees and flowers have begun to bloom (literally overnight) The fresh smell in the air brings happiness to everyone. (think I'm kidding? look at the ear to ear grins on everyones faces) That first day you roll down the windows on the way home from work is a beautiful thing.
Summer: It's quick, perhaps 3 months, but it is truly magical. Weekend beach trips, warm (usually not HOT) days, cool nights, sleeping with the windows open. Summer is a great treat. You will notice anything indoors sees a dramatic drop in business during these months as we Bostonians want to enjoy every moment of Summer.
Fall: New England in the Fall! There is nothing like it. Sure, we know Winter is not far off, but Fall has so many speacial treats. That first crisp day where you walk outside in the morning and feel a chill. The foliage, which changes daily (you can drive down the same street you drove down yesterday and the colors will be completely different) the smell of burning leaves...Fall is magnifigant.
Fondest memory: The first day of each season
... there are still a lot of things to do in Boston.
The Museum of Science (on a island on Charles River) is very interesting and for the little and big children (yes, me too) interesting.
The New England Aquarium at Central Wharf is worth a visit, too.
Go shopping or having a small bite in one of the many restaurants.
More museums: Computer museum, Children Museum, Boston Tea Party ship
Favorite thing: Upon our arrival on our second trip, it was literally too cold to snow. However, the night before our flight home, the temperature rose enough to allow the humidity to rise, and there was a fresh layer of snow on the road and cars at 4:45am, when we needed to head to the airport. Oh boy! Nothing like being the only car on the road, except for the snow plows and sand trucks.
Favorite thing: NOT MY FAVORITE THING: Boston gets COLD in the Winter. It's not just the cold that'll get you but the wind. If you visit in the Winter, bring hats, gloves and layers of clothing.