Layers:  Of course, everyone knows the trick to dealing with cold and varying temperatures during runs or races is layering.   About the only rule here is never wear cotton.  Wear a “technical” type top that wicks water away from your skin.  I have several “Coolmax” tops I wear most of the time in cooler weather. I have light weight ones for cool weather and heavy ones for cold days and nights.  I also have two “Hot Chillys" tops that I wear in frigid conditions.  The Hot Chillys are also the base layer I wear skiing on very cold days, cold as in sub-Zero temps.  If it is hot and I expect to be in the sun for hours I wear a very light weight, white, Coolmax, long sleeve top to block the sun.   There are other good options for layering, I just like Coolmax.

If I expect it to be fairly cold during my entire run or race, I wear a short sleeve Craft top as a base layer.  It is a thin, fitted top that is extremely warm.  I don't wear it if it will warm up during the day.  Over the Craft top I will wear a Coolmax layer.  If it is cold at the start I might add another layer of heavy Coolmax, or a layer of fleece.  I try to estimate what the temperature will be later in the day and dress so I can remove top layers and still be comfortable when it warms up.  I want to be able to pull layers off as needed and not have to take off a bottom layer.  To put it another way, start layering with what you want to end up wearing and end up layering with what you want to start with.

Suppose it is 28 deg at the start of a long race and the forecast is clear and 65 by mid day.  I would start with a short sleeve technical shirt under a medium weight Coolmax top.  I would probably not wear a Craft top because it would be miserable when the temperature reaches 60.  I would either wear a light jacket at the start or wear a pair of arm warmers.  I have a pair of Pearl Izumi arm warmers that I frequently wear in moderately cold conditions instead of a jacket, especially if there is no chance of rain.  They are available at any bike shop.  You can pull them down if it gets warm or pull them back up if it gets cool again.  I actually pull them up and down a lot.  It may be cold and windy on the top of a ridge and I pull them up.  As you descend into a valley, the hills block the wind and it gets warmer so I pull them down.  When I no longer need them they are easy to pull off without even stopping.  I just tie them somewhere if I think I will need them later otherwise I just stick them in the next drop bag.  Another popular brand among ultra runners is Moeben Sleeves.  They have a small pocket for storage on the side.  An extra pocket is always nice.

Socks: I wear two types of socks depending on how wet or dry I think the course to be. If I expect the trail to be dry and warm, I will usually wear “compression socks.” I use them for long ultras and the run segment of Ironman events. Read about the claimed benefits and consider a pair.  I have a pair of Zoot Compression RX socks and I like them.  Most makers of compression clothing also make Compression "Calf Sleeves."  I intend to get a pair of calf sleeves before Tahoe so I can combine the compression with Drymax socks, the other type socks I wear.   They are available in several weights and do a great job of keeping your foot dry in wet conditions. Earlier this winter I ran in wet, heavy, snow for about 4 hours of a 5 hour run. I had on a pair of heavy Drymax Trail Running Socks and my feet were never cold.   If you know your will have stream crossings in you run, they will help get your feet dry quickly.

Shorts: Take you pick. Wear what is comfortable. I like shorts with pockets. I usually wear one of two types of running shorts.  I wear a pair of Nike running shorts with deep side pockets much like an ordinary pair of shorts or slacks. They are great as long as you don't put too much stuff in them. When they get too full, they interfere with arm movement. The other shorts I use are called “RaceReady” shorts and have shallow pockets all across the back and side. The pair I have has 4 pockets across the back and two small ones on the side with Velcro closure.  Brooks makes very good running shorts, too.  A lot of ultra runners wear short length tights or triathlon tights.  I have not tried them.  I also like my Texas Longhorn, burnt orange shorts!!

Gaiters:This is one item I recommend to every trail runner. I wear them every time I set foot on a trail. And In my opinion, there is only one gaiter suitable for ultra running and I have three pair. They are “Dirty Girl Gaiters” and they are great. Follow the link to their web site and order a couple of pair. I have never had to stop and empty trash out of my shoes when wearing them. They weigh nothing and they are “dirt” cheep.  They are available in 60 or 70 patterns from plain to extreme.

If you cannot find the clothing or equipment you are looking for at you local running store try theZombieRunner website.  They specialize in ultrarunning gear.  That is why most of the links to specific item I provide are to Zombie Runner.