If you really fill like dipping your lines in something - go for the marine grade dry lubricant (SailKote for example). That stuff works great on the flying lines, depower rope and parts of the bridle that work with pulleys. Though it doesn't last that long.
On bars with the old-style strap-n-buckle trimmer it's worth giving these straps a nice wax-rub-job every so often, especially in salty water as these tend to stiffen up and jam.
I tried the sailkote option on my well used (sharpened) north bar, In 36 hours of water use my line was TOAST with some strands frayed to the point of being broken. Useless in my opinion The ski wax so far is over 100 hours on the same bar unmodified. I've meant to take a file to it. but things have been holding up so well I haven't bothered.
Sailkote may help with dirt accumulation, so it MIGHT be useful if put on from new. but if it's the bar that's chewing the lines it's still gunna fray. Wax seems to help no matter what the problem is.
With regards to temperature I looked up some ski wax melting points and you are cutting it pretty close using the really cold stuff as someone mentioned. Melting point of dyneema is around 140-160 C
Short durations of temperatures below that should not provide any decrease in breaking strength.
SOURCE: http://www.samsonrope.com/site_files/Ta ... imates.pdf
Some of the "cold" ski/snowboard waxes are around 120 C
some of the "warm" ski/snowboard waxes around 75C
Straight up parafin is 50-53C