April, May, September, and October are the best months to go sight-seeing in Barcelona. When is Barcelona less crowded? Barcelona is least crowded during the shoulder seasons of March – April and September – October.
What months are hot in Barcelona?
Summer. Generally the summer season lasts from late May or early June to late September or early October. July and August are the warmest months, with average temperatures around 28–29 °C (82–84 °F) during the day and 22–23 °C (72–73 °F) at night.