Mongolian weather is pretty much dry due to being isolated from oceans. But Northern Mongolia has forests, mountains, lakes and rivers which make it cool and pleasant. The summer is quite short and the peak season is from June to August and the average temperature is from +15C to +25C and some places like in the Gobi it will reach +41C. Late August is a little bit rainy and the Mongolian annual precipitation is around 210mm. Most of the rainfall season is a warm season.
Shoulder season is May and September and the average temperature is from +10C to +15 and this is the perfect time for fishing, and doing active hobbies like hiking & bicycling. Most of the Ger camps are open to May and close by September. This is also the most interesting weather period especially in some places like the Gobi, Altai Mountains, Taiga Mountains and some other places. During your activities, it might show you all 4 seasons in 1 hour. It rains, hails and snows and then the sun shines brightly. Now you have an idea about what kind of clothes to pack.
By the end of October through April the winter reigns through the whole country and the temperature would be 0C and then drops down to – 25C and some places it goes down to -40C. But nomads survive and continue their herding and camp at their winter corals. Few Ger camps operate all year round and adequate tours and activities would be skiing, dog sledding, or visiting nomad families up in Taiga Mountains or in their winter place.