The city receives 511.5 millimetres of precipitation a year and 2,046 hours of sunshine, figures typical of a moderate continental climate. But the distribution resembles almost no other city at a similar latitude, and that distribution completely inverts the logic we normally use to choose dates.
01 The rain runs backwards
The numbers in a row: 16.4 millimetres in January, 18.2 in February, 29.1 in March, 63.8 in April, 82.9 in May, 84.0 in June, and from there it falls again: 41.6 in July, 39.4 in August, 34.8 in September. It is a curve with a peak in late spring and a trough in midwinter, exactly the reverse of the Mediterranean.
02 Winter is dry and dark
January and February are the least rainy months of the year, and that may sound like good news. It is not. January totals 99 hours of sunshine in the whole month and December only 93: that is, about three hours of sun a day. Little rain does not mean clear skies; it means stable cloud without precipitation.
And it is genuinely cold for a city we tend to picture as temperate: an average high of 6.9 degrees in January and a low of −0.6, with regular night frosts. In a city of steep slopes and open-air staircases, that shapes the walking far more than the rain does.
03 The valley overheats the summer
Summer has the sun that winter lacks — 256 hours in July and 248 in August — and considerably less rain than May or June. The problem is the heat and, above all, where it accumulates: the city occupies a narrow valley with slopes on both sides, and that funnel traps hot air at the bottom, exactly where the historic centre is.
July has 256 hours of sun and December 93. It is the same city with less than half the light.
In exchange, the height difference works in your favour: there are almost four hundred metres between the lowest and highest points of the municipality, and going up the slopes genuinely changes the temperature. That is the practical reason why, in summer, it pays to organise the day backwards: the low district first thing and height in the afternoon.
04 The September window
September is the month that resolves the calendar's contradiction. It has a high of 26.2 degrees and a low of 15.9, exactly the range for walking all day and eating outdoors at night; 34.8 millimetres of rain, less than April, May and June; and 206 hours of sun, eight times a winter month's.
October is the second option and has its own argument: a high of 20.0 degrees, trees in colour and 46.3 millimetres, a little more water but spread out. From November the light collapses — 103 hours — and the city enters its grey stretch, which lasts until March.
05 The verdict
September, with room to spare. It is the only month that combines a comfortable temperature, little rain and plenty of light, and it also falls outside both the heat peak and the rainfall peak. The second half is better still than the first, because August's heat has fully eased.
And the advice that corrects the commonest mistake: do not come in May for the temperature. On paper, a high of 23.7 degrees looks like the perfect month, but May is the year's second wettest, with 82.9 millimetres. In this city, the column to read first is not the thermometer's: it is the rain gauge's.
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