You will have to bring along your own sleeping bag when on long journeys that involve camping.  During cold spells early and late in the season, there is a slight chance of night temperatures below zero centigrade.  Frost is unlikely - but happens – even in the summer. 
A four season sleeping bag is definitely necessary early and late in the season.  If you feel cold easily, or your body is small, you should take some care in the selection of your sleeping bag. 

Yak trek camping at Terhiin Tsaagan Lake in Arhangai July 1993. 
This lake holds a lot of quite large Siberian Pike that prey on ducklings, 
which is why this lake is quite devoid of water birds.

If you have never slept under the stars. 
Don’t worry! You will find it a real pleasure.