מזג האוויר בבייג'ינג בדצמבר

Regulars are consistent this is warm but clearly a step below the real peak, July and especially early August, and specifically call this dry-climate heat more manageable than the humid version found further south in China. Our row backs the intense but dry heat, 33.3C reading as a real 33C, over 19.3C nights, with 44.5mm of rain across 6.4 days and humidity down to 47 percent. Regulars are clear rain here, even in the wetter summer months, essentially never means continuous days-long rain the way it might elsewhere - more chance of a shower, never a washout. This month sits inside the wider window, alongside September and October, that regulars call the best overall stretch to visit, avoiding the big domestic holiday crowds. The record: 11.1 hours of sun, a 14.6 kph wind and AQI 122.

Regulars are reassuring on the sandstorm question specifically: they're rare, don't happen every year, and are more a risk in April than March - and even on the rare day one does roll through, sleeping past nine or ten usually means missing it entirely. Our row backs a dry, sunny-leaning month overall, 16C reading as 12C over a real -4C-feeling low, with just 10.1mm of rain across 2.9 days and a trace of leftover snow, 1cm. Regulars note that on the handful of days it does rain, the air actually clears a bit rather than getting worse - a useful exception to the column's AQI figure of 139, since a rainy March day is one of the better-air days rather than a worse one. The record: humidity 47 percent, 9.7 hours of sun and a 14.7 kph wind.

September is one of the two months regulars recommend here and the weather half is unarguable: 28.2C days over 15.8C nights, 53.6mm of rain across 5.3 days, and the crowds thinner once schools go back - though the first week of October is a national holiday and should be avoided. On air they say September is not bad compared with winter and that October is better still. Our column only half agrees: 155 this month, the same in October, against 122 in April and June. Winter is certainly worse at 183 in December, but the cleanest air here belongs to spring. They are right that it changes day to day. The record: humidity 64 percent, 9.6 hours of sun and an 11.5 kph wind.

May is one of the two months - October is the other - that Beijing regulars name as the year's best: the muggy summer has not arrived, and they give a range of about 12 to 28C, which our row's 13.3C nights and 29C days match almost exactly. The cautions are seasonal rather than daily. Sandstorms, smog, haze and the occasional burst of real heat are all things May sometimes does, and our row's AQI 127 is the standing version of that. The dates to plan around are the Labour Day holiday, roughly the 1st to the 5th, when regulars say to keep away from the sights altogether; mid to late May is the quieter half, though the end of the month is normally busy. The record: 23.2mm across 4.2 days, humidity 42 percent and 10.8 hours of sun.