What makes a fishing season?  

I imagine this varies from angler to angler, and river to river.  I'm a New Englander, and I tend to  think of the fishing year in several parts:  

Westfield River July 1 2011.

Spring season, when stream flows,  water  (and air) temperature, and clarity allow nymph or streamer fishing.  Often uncomfortable, but worth it after a winter away from the water. I don't fish this season as much as I used to, years ago - work and other chores getting in the way.  I remember back in the 1970s,  I would pick a reasonably pleasant day in March and head to the Westfield River.  I could usually count on catching at least one brown trout, of decent size (15" or so) that appeared to be a holdover.  This would be before the stocking trucks started rolling for the year. Later on, still in spring season, but after the new arrivals, the numbers would increase. I remember another day catching 22 fish, all but one on streamers, and mostly rainbows, in the same stretch.

Dry fly season.  Usually beginning sometime in May on the New England rivers I fish.  This can be very short on some rivers, such as the Millers, which can get well up into the 70s (Fahrenheit, of course) by early June in some years, mid June in most.  On the Deerfield and Westfield, my last visit for the season on the non-dam stretches is usually early July.

Skinny water on the Westfield River, July 1 2010 meant careful stalking, tough fishing. A year later, same date, water levels were great, fishing was easy.

Tailwater season. After the free flowing stretches of most local rivers get too warm to fish, I limit my fishing to the reaches below dams with coldwater releases: Deerfield, Swift, and the occasional trip down to the Catskills.  Back in the 70s and 80s, I used to fish the Battenkill regularly, and could depend on fishable conditions during all but the hottest of hot spells.

Fall season.  When waters are cool enough again, fishing on some rivers comes back to life.  How good the fishing is seems to depend on several factors.  One important one is how wet the summer has been. On rivers like the Millers, with a lot of tributaries that appear to serve as summer trout refuges, a wet summer (and sufficient water in the tribs) can mean good fall fishing.  Conversely, I suspect the Westfield River doesn't fare as well through summer doldrums, because it appears there are few tribs that trout can use to escape the heat.   Then there are the rivers that receive fall stocking of trout.  I'll fish for them, but summer holdovers are a preferred quarry.  Fall season usually ends for me sometime in November, although once in several years I might spend a couple of hours on stream on a forgiving early December day.  

Putting the season to bed.  I don't fish during the winter.  There's something about snow on the banks that tells me it's time to trade the rod for the pole - and make sure I have the right wax on my skis. 

Are our fishing seasons changing because of climate change, or for other reasons (e.g. land use change)?  Is the trout season getting squeezed into fewer viable fishing days nowadays? If so, are high stream temperatures the only limiting factor?  It seems to me, albeit with only  anecdotal evidence & personal experience to back me up, that the spring season may be getting compromised also.  It seems like we're getting a lot of high flows during some of the better traditional hatching periods - more so than in years past.  Many a day I've planned to go fishing in April, May or early June, only to cancel because the river's blown out. 

What's your experience?  Do you have a personal calendar for each river you fish?  Does it seem to be changing? If so, why?  And what's your opinion on spring flows? Do they seem more variable or problematic for fishing than they use to?