September might be the most underrated month in Stockholm. Summer crowds have thinned out, but the weather is still genuinely pleasant — average highs of 15–17°C in early September, dropping toward 10°C by October. The city turns a deep amber and rust as the leaves change, particularly spectacular in Djurgården and along the waterways of Södermalm. Hotel rates drop noticeably from late August onward, and the pace of the city shifts from holiday mode back to something more everyday.
Rain becomes more frequent through October, so pack layers and a waterproof. The approach in
Sweden is essentially to dress for it and get on with things — there's no such thing as bad weather, and all that. Stockholm's covered market halls like Östermalms Saluhall are a good wet-weather option, as is the Nobel Museum in Gamla Stan.
Autumn day trips by trainAutumn is excellent for rail day trips to the Swedish countryside. Uppsala's cathedral and university town feel atmospheric with the autumn colours, and the 40-minute SJ regional train from Stockholm Central runs frequently throughout the day. Further afield, Lake Mälaren, the large lake that Stockholm essentially sits on, is ringed by castles and manor houses reachable by regional rail and ferry. Mariefred and Gripsholm Castle are worth a half-day.