You go out on your mid-March ride on a day with light overcast skies and slightly cool winds.  You are dressed appropriately  if a little on the warm side on the count of your apprehension over leaving the house.  Your ride starts as normal and you begin to warm up.  It is not long before you are wishing that perhaps you had one left the jacket at home or worn the lighter tights.  Then, the real trouble hits you as the sun starts to peak out from the clouds turning slightly warm to boiling.  Everyone has had this happen and to be sure it could just as easily be the reverse of this situation.  i.e. cool to freezing.  What you may not realize, mostly because there is not an abundance of choices available, is that your clothing is not inter-season wear. 

What is inter-season clothing and why do you need it?  Inter-season clothing is not just lighter weight winter clothing or heavier weight summer clothing.  It's definitely deserves its own category.  It is clothing that often incorporates layering schemes while also focusing on high-performance water resistance, extreme breathability, and at times, convertibility.  To facilitate the moisture transfer properties of inter-season clothing, a thin high-performance wicking base layer is nearly always recommended.  The goal of all this is to make clothing that provides comfort and optimal performance over a broad range of temperature, humidity and wind conditions.  

So, why isn't your clothing good enough for to keep you happy in varying conditions?  I suppose that mostly, the reasons for this are that few shops or online retailers do a good job of stocking or marketing these items.  To be exact, the majority of stores would not know or care to order them.  Many of the shop owners and buyers do not ride seriously or all-year round, or in some cases at all.  And as such, could not possibly relate to the need for higher performance transitional clothing.  Still, more of them are motivated by a wag the dog scenario in which they order only what is appears to be in demand, a demand that is created by customers that do not realize that they have alternatives in their gear choices.  Whats more?  Far too many shop owners and buyers are removed from the sales process and have no interface with cycling enthusiasts.  When a shop owner would be as happy if not more by selling any unnamed commodity as selling bicycles, then he has made the switch from a cycling enthusiast to a general retailer.  You might want to ask yourself, in this case, if you are buying from the right guy?  Sadly, this is the case for the majority of shops and shop owners.  They lack passion for what they sell and so they haven't engross themselves in to the technical aspects of the products they sell -- tending instead to push what is profitable over performance, and you end up with an inadequate array of products.

On the issue of breathability, special fabrics must be used to provide a greater degree of moisture transfer through the outer shell of your garments.  Where a winter jacket might have to keep out moisture and breath in relatively low temperatures from 32 to 45 degrees.  An inter-season jacket will and does the same job for a range of temperatures much greater.  It might have to maintain comfort up to 55 degrees or more.  Through the use of advanced fabrics and DWR finishes as opposed to three layer gore-tex™ types.  Breathability is also enhanced via strategically placed vented paneled air vents.  

Greater ability to handle temperature changes for a pair of inter-season tights is handled by using a thinner fleece backed Lycra™ without a waterproof layer.   The fleece layer uses hollow fibers for superior warmth.  When combined together, this equates to tights with excellent breathability and the ability to hold heat far surpassing that of many thicker tights.  It is striking how layers like this can keep you warm through a broad range of temperatures.  I have a pair of Campagnolo Raytech inter-season tights that I can wear comfortably in temperatures ranging from 45 to 60 degrees without any overheating or over cooling!  They are really impressive. 

With the addition of a good light weight base layer, the inter-season ensemble is complete.  In this case, the goal is extreme wicking ability and ultra quick evaporation of liquid water coming off of your skin.  Thin base layers are best at this.  The addition of an ionizing material such as silver filaments (preferable) or carbon fibers (that's right they even make carbon fiber clothing) aid in ultra quick evaporation by pulling more blood to the capillaries close to your skins surface effectively raising your skins surface temperature.  It is a small increase, but it is enough to speed evaporation improving the evaporative cooling effect.  It is interesting to note that with winter clothing a base layer is worn to increase warmth, contrastly, with inter-season clothing, the idea is to increase cooling.  In general, your body temperature is maintained in the inter-season mainly by this evaporative cooling effect,  You are kept from over-cooling by the careful placement of windblocker type fabrics in areas facing the wind.  This works incredibly well.

Do you really need inter-season clothing?  In some cases, maybe not.  You may be getting along fine with what you have and it may seem frivolous to buy more.  I suspect in most cases though, you might not know what you are missing.  Being able to ride in such comfort over such a wide range of conditions is really enjoyable and to me makes the ride sweeter.  You have enough to deal with in watching for road hazards, focusing on perfect pedaling form and dodging irate drivers.  is it really worth it to be uncomfortable as well.  Inter-season clothing may be more a necessity then you might think.  

So you know you need it but where do you get it?  Here in lies the problem.  Inter-season clothing may not go by this name.  It may be hidden within the winter and summer lines for certain manufacturers.  Virtually every clothing manufacturer will make clothing that fits this category.  To find it, you might have to do your research a bit.  Look for fabrics that have the characteristics that I just mentioned.  Most manufacturers will have information on their web sites or attached to the individual garments that describe the functionality of their technical fabrics.  Some even include a temperature range for comfort.  If they do, look for items who's temperature range falls in the 40° to 60° Fahrenheit.  Until the day that manufacturers start to label these clothes as such, you will have to bone up on your technical fabrics characteristics.  Hey, it is not as if this is a new thing.  In cycling, and in all technical activities, there is always a maze of product to sort through.  Here it is no different.  However, it is a maze well worth traversing.