How do you choose the right wax without measuring the temperature of the snow?
For best results, we always recommend measuring the snow temperature with a thermometer or laser, however we appreciate this isn't always practical! So the big question is, is there a way to predict the snow temperature in advance from the air temperature?
There are three different factors to consider; snow temperature, air temperature and humidity. Air temperature can be used as an indicator for how the snow is going to change. If the snow temperature is -10°C and the air temperature is +5°C, you can be confident that the snow will warm throughout the morning and vice versa.
There is an event on starting at 8am one Sunday. The overnight low from the previous night was -15°C with a forecasted high of 2°C on the day of the event. The air temperature at 8am will probably be around -4°C. However the snow temperature would most likely be closer to -12°C first thing in the morning, because snow warms far slower than air. This warrants our blue wax Butane, for early morning, but might change to our red wax Magma later in the day as the snow warms above -8°C.
For the best 'all-day' experience: aim to wax for a temperature half way between the overnight low and the forecasted high for the day.
For early morning competitions: general rule of thumb is a few degrees above the overnight low from the previous night.
To be specific, consider the overnight low. Then consider the forecasted high of the day and what time of day it might reach this high. Also consider whether or not this temperature will be everywhere or only in the sunny exposed areas. Try to guess the air temperature for when you might be competing (somewhere between these two numbers). Then consider again the overnight low and the air temperature for when you anticipate competing. Somewhere between these numbers, probably closer to the overnight low number, will be the snow temperature for your run. That's the temperature that you should wax for.
The one major exception is if precipitation is anticipated. In Europe, precipitation is generally "wetter" and acts "warm" therefore requiring a warmer wax. In Canada, Japan and particularly the Rockies, when precipitation is "dry" (even at warm temps) it often requires a colder wax than the temperatures would indicate, due to the harsh snow crystals formed needing a harder wax.
Bottom line is that snow temperatures are quite predictable if you know the overnight low, the competition start time, and have a feel for what the air temperature might be for when you are competing. The combination of the snow temperature and observing what kind of crystals are present (corn, powder, etc) give you the most important information needed when determining what wax to use.