Het weer in Ulaanbaatar (Ulan Bator) in september

Regulars are specific that a first, brief snowfall typically arrives around mid-month, lasting just a day before conditions warm back up again - a genuine marker of the summer-to-autumn transition rather than the start of real winter. Our row backs that mild-by-day, genuinely cold-by-night read, 17.4C over 2.1C nights feeling -1C, with 42.6mm of rain across 7.6 days and a trace of early snow, 5.1cm. Regulars are consistent early in the month brings comfortable daytime temperatures around 20C with plenty of sun, even as nights already turn genuinely cold enough to need real warm layers. This remains a workable month for the countryside and national parks before deeper winter sets in. The record: humidity 64 percent, 9.7 hours of sun, a 16 kph wind and AQI 36.

Regulars call spring and early summer the hardest stretch of the year to forecast here - warm enough in the Gobi and not especially cold in the north on a good day, but capable of dropping below freezing with rain or even snow with little warning. Our row shows exactly that volatility rather than a settled month: 17.8C by day but only 14C in the wind, against 1C nights that feel like -3C, with 7.3cm still in the snow column and 24.5mm of rain across 4.9 days. The real season here, regulars are consistent, is June through September; May gets you dust on the steppe and a Lake Khuvsgul still frozen over, which suits a specific kind of trip more than a typical one. The record: humidity 44 percent, 12 hours of sun, a 19.6 kph wind and AQI 46.

August is the wettest month of the Mongolian year and regulars treat that as the price of the scenery: the rain is why the landscape is green through the summer, and the season runs June to the end of September. July is the hot, reliably sunny one, past 30C; August cools, and September cools further with more rain. They put the gap between day and night at about fifteen degrees, with nights near 15C early in the month - our row has 22.5C over 9.1C - and warn that snow can fall late in August or early in September. Our 79.3mm falls across 12.4 days. The record: humidity 69 percent, 10.5 hours of sun, a 14.1 kph wind and AQI 38.

June is inside the Mongolian summer, which regulars date from late May to mid-September, and the figures they give for Ulaanbaatar - 20 to 30C by day, chilly once the sun goes - are our row's 23.6C over 8.1C almost exactly. That night figure is the whole packing problem: the day can feel like shirtsleeves and the evening reads as 6C. Out in the Gobi the same gap opens wider still, hot by day and cold at night, and the advice is layers plus something genuinely warm rather than a jacket chosen for the daytime. Several regulars prefer September to June for the desert itself. Our row also carries 0.8cm of June snow, which is the high ground in the grid square rather than the city. The record: 47.7mm across 9.3 days, humidity 53 percent, 12.1 hours of sun and 16 hours of daylight.

Ulaanbaatar forum threads describe February as one of the coldest months of the year, with posters citing a range as extreme as -25C to -55C in the harshest conditions, though a more typical winter stretch was described as -20 to -35C. The air was flagged as genuinely arid despite the extreme cold, which posters said makes the chill feel slightly different than a damp cold of the same number. Posters were consistent that the bitter cold doesn't rule out a real visit - a well-prepared multi-layered, fur-lined or fleece-inner jacket plus thick, high-grip boots for icy streets were the standard packing advice, and posters specifically recommended February's ice festivals, including the one held on Khövsgöl Lake, as a genuine highlight of the season rather than something to avoid.