Surabaya weather in September

Forum posters describe January as squarely within Java's rainy season, with a real chance of rain especially at higher elevations, though conditions stay genuinely variable - a lucky morning can be dry, with rain more typically starting around midday. Posters describe the wet-season pattern as usually bringing rain in the late afternoon or overnight, intermittent rather than constant, so an umbrella is generally enough to keep plans on track. Posters visiting nearby Mount Bromo specifically note a real trade-off: only a 10-30% chance of a clear sunrise in January, but far fewer tourists and more of the site to yourself as a result. Posters generally rate January as manageable for a Surabaya-area visit with realistic expectations and rain gear on hand.

Forum posters describe July as squarely inside East Java's dry season, with Surabaya itself hot and humid - posters call it one of the hottest cities in Indonesia. July also lines up with peak season for the popular Mount Bromo and Ijen day trips from the city, though posters flag a sharp contrast at altitude: temperatures at the Penanjakan viewpoint above Bromo can drop to 4-9C for sunrise, cold enough that many visitors skip the viewing point rather than brave it. Posters recommend packing a mask for dust given the dry conditions, and note Ijen's crater can occasionally close depending on volcanic activity, so building flexibility into a mountain-focused itinerary from Surabaya is worthwhile.