מזג האוויר במוסטאר בספטמבר

September is the month regulars recommend on this island and their reasoning is about lag: the crowds of June and July have gone but the sea is still carrying August's heat, so swimming is as good and sunbathing better for not being too hot. A sweater in the evening, they say, and certainly not a coat. Our row agrees on the sea at 24.5C against 25.5C days and 20.3C nights. It adds the thing the board does not discuss: 116.3mm of rain, which falls across only 8.5 days at fourteen millimetres each. That is the Adriatic September pattern - long fine spells broken by real storms - rather than the drizzle the total might suggest. The record: humidity 71 percent, 10.4 hours of sun and a 16.9 kph wind.

Forum posters describe Mostar's southern Herzegovina location as giving it a noticeably milder winter climate than northern Bosnia, with snow uncommon here - wind and rain are more likely worst-case scenarios for a December visit. Posters generally describe Bosnian winters as trending milder in recent years, though genuine surprises remain possible. Posters consistently note that the road into Mostar is well maintained and kept clear of snow even during winter weather elsewhere in the country, with rental cars typically supplied with snow tires as a precaution regardless. Posters generally rate December as a comparatively mild, manageable time to visit Mostar relative to the rest of Bosnia and Herzegovina, wind and rain the more likely weather challenge than snow or ice.

Mostar is the hottest place in Bosnia and Herzegovina — too far inland for the sea to cool it, and on a Mediterranean rather than a mountain climate — so June here reads very differently from June in Sarajevo. Days average near 28°C and the forum reports spells reaching 35°C; nights fall to about 16. The other June problem is size: the old town is small and gets completely crowded, with day-trippers off the Croatian coast and pilgrims bound for Medjugorje on top of everyone else. Regulars' fix is to stay overnight rather than day-trip, which also opens up Blagaj's dervish house and river source, and the castle town of Počitelj.