Despite some rain, March through May and September through October is deemed the best time to visit Brussels. Accommodation is cheaper to book and tourist crowds are thinner at this time. Spring or early fall is perfect for enjoying the Brussels Jazz Festival or rocking out at the Horst Arts & Music Festival.
Summer promises a load of unforgettable events like Foire de Midi or Flower Carpet & Flower Time. But, it also brings long lines, crowds of tourists on the streets, and skyrocketing prices. Even though it tends to be chilly and wet, the time between November and February still faces high rates in terms of holidays. Just don't forget this is also a high time to taste traditional Jenever and to feel like a local at Aalst Carnival.