As far as the Scout board itself is concerned, all electronic components are rated for at least -20°C to +70°C operating temperature--the 16MHz crystal being the most sensitive component on the board, due to ppm drift based on temperature changes. It's rated at no more than 25ppm at those extremes--but if you're willing to put up with more ppm drift, you should be able to exceed the temperatures up to industrial (-40°C to +85°C.)
The power switch is rated at an operating temperature of –10°C to +60°C. If you wish to bypass this switch with something more robust, there are two 0.1" holes underneath the switch that you can solder to, to bypass this switch.
Lastly, Lipo battery chemistry will suffer capacity issues much more at lower temperatures, with up to 50% capacity lost at 0°C. For this level of temperature, you may want to consider alternative power methods such as supercapacitors or external power. The battery jack also has two 0.1" holes underneath to bypass the battery with an alternate power source.
Hope that helps!