basically the risks associated with housing juvenile bluetoungues outside during there first winter are as follows:
*temperatures may reach such a low level for such a long period of time that important functions may not work e.g. immune system and digestive system.
*if they do begin to lose interest in food then growth may be stunted
*unless the enclosure is covered the may fall prey to larger animals like cats and large birds
just generally it is believed safer to keep them inside due to the risks involved but it seems as though you have taken several precautions so i think that it should be fine as long as you keep a very close eye on them. also something to think about, a few days ago there was a topic about outside enclosures where the idea of a thermostatically controlled heat cave could be used on cooler days.
good luck,
keeth
