I'm in the Hudson Valley in NY and I keep my kayaks and canoe outside year-round. They are upside down on a rack with no cockpit cover or other covers. I have found with cockpit covers that rain runs around the edges of the coaming and pools in the cover. The weather does affect the varnish some but that is to be expected. I usually revarnish every couple of years anyway.

Dan

   I left my Passagemaker in coastal Maine outdoors two winters ago, covered with a tarp upside down on the trailer and it was not noticeably affected by the snow, rain, freeze/thaw.  I think that the key is to keep it off the ground, and let air circulate under it.  The bottom is painted, so UV wasn't an issue, but hey, I had the cloth cover and the tarp so why not use them?

One issue I had with outdoors storage in the Sacramento delta one year was raccoons, who fouled it up something fierce.  Nothing washing couldn't deal with, but not nice.  It was on the ground, not fully upside down, leaning on something, plus I had left the large hatch to the forward compartment open, so perfect as a lean-to with a custom den!  

   Covered too tightly, is more of an issue in summer. It becomes a steamer.  I had to strip and re epoxy one build I left in a Canoe storage bag. I have have a 21 foot clc tandem stored outside for 25 years.  It does not look great but still works fine.  I wouldn't do it to one of my recent builds.  I cover with venting it is the best I can do.  And yes seal openings where raccoons might move in. 

Jim, I keep my Exp Wherry outside just like you mentioned, for years - upside down, about 3 feet off the ground on sawhorses.  I've got a tarp over it, the ends of which are only loosely cleated underneath it, to keep the tarp from blowing away, but loose enough to let air infiltrate.  The only downsides are spiders and whatnot trying to make a home in the thing - not a big deal.  This is up in northern PA.  Up here I have found that epoxy coated stitched and glue boats which are painted, do not lose any structural integrity, season to season, when left outside, but protected, year round, from rain and snow, by weather tarps, though every few years it is necessary to replace the tarps.  

Mind the cheap blue poly tarps--they have a habit of flogging their blue color onto your boat.  I've been using heavier white tarps from Tarps Plus and been pretty happy with them.

.....Michael

I  purchased WeatherMax80 irregulars from EBay.  I use the material to cover motorcycles, cars, kayaks, NED.  This is same material CLC Kayaks use for their covers.Take a look at CLC boat covers.  Waterproof for many years and UV resistant for many years.  Must do some sewing.  I use lifetime thread that is UV resistant.  Do it once and it lasts for years.  

   I looked up your boat and it is only 3' beam.  I got killer deals for a lot of WeatherMax80 material.  At 60" wide would only need the correct length.  I purchased complete lengths irregular material on roles so it did not need to be cut.  It was very cheap.  Currently looks about $7 per yard.  The seller that I purchased from has not restocked.

I looked at CLC boat covers.  I noticed a spar bag.  I will make one longer for my mast with WeatherMa80.

 Somewhere there are specifications on WeatherMax 80 that tells how breathable it is, how long it is waterproof before having to clean and retreat it and UV resistance.

   I've had some luck looking for heavy-duty tarps for my boat for storage in the winter recently. They work great. I use the heavy poly ones for my boat.