On a day like today...
Admittedly, two months ago I would not have called 45° cold; especially on a day with blue skies, calm winds, and a bright sun. In fact, one particular ride not so long ago, we were joking about how relieved we were that the weather was so nice: partly cloudy and 40°.
Today is different.
1.) Acclimation (or acclimatization) is the process by which we gradually adjust to our environment. That's why a 45° day in winter is balmy while in summer it would be down right "freezing!" Our bodies can adjust to the weather to allow comfort, but our bodies need a good bit of time to make that adjustment. Each person acclimates at a different pace, and the amount of change (i.e. difference between your comfort level and what you are trying to achieve) determines the amount of time a person will need to fully acclimate.
Riding on cold weather days leading up to the Assaults means that you will handle the start well. However, it may mean you will hit the wall in Marion, where temperatures are often in the mid-70s.
2.) Today is much like the Assaults: a huge swing in temperature. A 25° shift in the air temperature is tough on the body - made worse when it's 45-70. There is a much more significant difference between these temps, considered cold and warm, whereas a swing between 0-25° or 70-95° is less so - we dress either very warmly or strip it all off... and that's it.
Starting out in chilly and ending in warm temperatures means we have to bundle up and peel as we go. Our pockets will be over-flowing with warmers, vests, food, phones, etc. We may not be able to handle all the extras, so be sure to consider every article of clothing carefully.
Starting out too cold can lead to tense muscles, wasted energy, or worse: injury. Whether your tight muscles don't give, and you tear something or your shivering causes you to crash... it's just not safe to be "cold" at the start. That said, being "a little chilly" is ok - in fact, it's good. You will warm up, and you will begin to strip off layers, so it's best to save a little space by not wearing too much at the start.
In general, you should not need to pull off layers in the first 45-75 minutes, no matter how hard you are riding or how quickly the temperatures rise.
3.) So what is the best way to dress for this event? Layers. We've all heard it, but what does it mean? Unfortunately, it's different for everyone, but there are some general guidelines to go by. Here is a link to a "What to Wear" chart, which is a good place to start:
This is a good catch phrase: "If it's below 60 degrees, cover your knees!" That's a good starting point, but as ever, "Know thyself." The key to success in these events - in all aspects - is to know your own limitations and needs (nutrition, hydration, clothing, climbing speed, etc).
So, use this as a guide and then experiment. Try out different combinations to see what works best for you... and keep trying things out as the seasons change, as you buy new clothing, as you get stronger, and as you get older! (I definitely don't dress the same as I did 5 years ago.)
4.) Practice changing clothes on the bike. Practice peeling layers while rolling and stuffing them into your pockets without getting those pesky sleeves caught in your spokes! Practice putting them back on. Practice all of these things away from everyone else! Whether it means you only do this stuff on your solo rides or it means you drift off the back of the group to make a quick change, don't try to "go pro" right in the middle of the pack: way too dangerous!
4.) Disclaimer: yeah, so the Assaults are like none other. No one knows what the top will hold. Some years, it has been in the 90° range at the finish, and others it has snowed (both of these are possible in the second week of May!). We usually start around 50°, reach mid-70s in Marion, with temperatures steadily dropping as we climb skyward.
The best way to prepare for this kind of change is to watch the weather stations carefully and make an educated guess... then pack accordingly. A friend of mine always said, "It's better to have it and not need it, then to need it and not have it." That holds true in a lot of ways - but use common sense, too. Don't carry a fleece-lined, rain jacket if the forecast is 80° and sunny.
5.) Disposable Warmth. If the temperatures are going to skyrocket, but are just too cold to bear at the start, I will sometimes wear "disposable" layers. I might put a strip of plastic bag under my Armskins or Slipstreams (which are good down to ~45°, but breathe in such a way that particularly cold days can be too light).
This is a lot like the Pros who grab a newspaper at the top of a long, cold descent. It's meant to keep off the chill, but they will dispose of it rather quickly (without the need to put it back on). I don't do this on most rides - but sometimes I will put that little bit of extra wind protection on just for a little while.
Two things to remember though: 1. Make them extra easy to remove (usually, I can just slide it off my arm while the Armskin stays in place); 2. please, please, please Dispose of them properly. Throw them in a trash can or something like that - dropping it in the road is bad for the environment, but worse for the guy behind you who now has a plastic bag stuck in his rear derailluer!
It's difficult to prepare for major changes in the weather, but with forethought and practice, a cyclist can be completely comfortable on game day.