The city receives 455 millimetres of precipitation a year and has an annual mean temperature of 11.6 degrees, figures typical of a moderate continental climate. What throws you is not the amounts but the distribution: the rainfall curve looks nothing like the one we expect in the northern hemisphere.
01 The rain goes to spring
The curve, in a row: 28 millimetres in January, 36 in February, 48 in March, 71 in April, 59 in May, 34 in June, 19 in July, 15 in August, 18 in September, 37 in October, 45 in November and 37 in December. There is a clear peak in mid-spring and an equally clear trough at the height of summer.
02 A real winter
Winter here is serious and should not be underestimated. January has an average high of 2.9 degrees and a low of −7.1; February, 5.1 and −4.9. And the records of the series, which begins in 1936, are −31.9 degrees in January and −34.0 in February: on an open continental plain, an incursion of cold air meets no obstacle.
There is also a factor that does not appear in the table and that affects health. In winter, with stable, windless air, the city's air quality degrades noticeably, and that is the main reason not to plan a trip here between November and February if you have asthma or respiratory allergies.
03 Summer is dry and works in tiers
July and August are the year's dry months: 19 and 15 millimetres, with average highs of 32.4 and 31.4 degrees. On the plain that is real heat, and a city of broad streets and open spaces gets hard between midday and five, even with the tree cover it has.
But here there is an escape almost no destination offers: altitude. The range begins a few kilometres away and climbs four thousand metres, so half an hour uphill by car is worth ten or twelve degrees. In summer the sensible plan is not to dodge the heat by timetable but by elevation.
July gets 19 millimetres and April 71. The dry month is the hot one and the wet month is the beautiful one: you have to choose.
04 Autumn resolves the contradiction
September is the month that brings together what the others have separately: a high of 25.6 degrees and a low of 11.7, the range for walking all day and eating outdoors, and only 18 millimetres of rain, practically the same as August. July's heat has gone and October's water has not arrived.
October is the second option and adds the colour of the trees, which in a city this heavily planted is a spectacle in itself, at the cost of doubling the rain to 37 millimetres and dropping the low to 5.6. From November the window closes: a high of 10.3 degrees, night frosts and the air starting to load up.
05 The verdict
September, with room to spare. It is the only month offering a comfortable temperature, reliable skies and mountains still accessible before the first high snows, all at once. If the trip is mostly about the city, the first half of October works just as well and with the trees in colour.
And the warning that corrects the commonest mistake: do not pick April or May on temperature alone. On paper, 18.7 and 24.1 degrees look perfect, but between those two months 130 of the year's 455 millimetres fall. In this city the rain column and the thermometer point in opposite directions, and you have to decide which matters more to your trip.
