Jun 17, 2018 - 11:25 PM
A down jacket is probably not needed. I usually just wear a t-shirt, long sleeve shirt, fibre pile vest and my rain jacket. Inside the Ice Palace the temperature will be below freezing. Outside on the plateau the perceived temp will depend on the wind, so if you can keep the wind out, you'll be OK.
If you are having trouble converting Celsius to Farenheit, just add 15 and double, so 0 Celsius becomes 30 Fahrenheit. Not exact, but close enough.
Also, make sure you have sunscreen on if the weather is sunny. The combination of snow and altitude really increases the amount of UV radiation you will be exposed to and you will get sunburnt quite quickly. Watch out on slightly overcast days as well. Thin clouds don't offer much protection from the sun.