European Quarter in June

April through June gives you the best weather without the tourist crowds that hit Grand Place. The European Quarter actually feels more alive during EU session weeks - check the Parliament calendar before booking. September and October work perfectly too, with mild temperatures and the diplomatic community back from August holidays. But here's the insider tip: visit during a plenary session week in Strasbourg (usually one week per month) when Brussels empties out. You'll get better restaurant reservations and shorter lines at the Parlamentarium. Winter months mean shorter days and more rain, but hotel prices drop 30% and you'll see how the quarter really functions when it's just locals and civil servants going about their business.