Belgium has two good windows: May–Jun and Aug–Oct. They sit either side of the season the climate record rules out, which is why the shoulder months matter here. The recommended window is Apr–Oct.
Mild; summer warm & busy
| Month | High °C | High °F | Rainy days | Verdict |
|---|---|---|---|---|
| January | 5.4 | 42 | 44% | Fair |
| February | 6.8 | 44 | 44% | Fair |
| March | 10.6 | 51 | 37% | Fair |
| April | 14.6 | 58 | 35% | Fair |
| May | 18.3 | 65 | 39% | Go |
| June | 21.0 | 70 | 42% | Go |
| July | 23.2 | 74 | 45% | Fair |
| August | 23.1 | 74 | 43% | Go |
| September | 19.9 | 68 | 41% | Go |
| October | 15.2 | 59 | 41% | Go |
| November | 9.7 | 49 | 47% | Fair |
| December | 5.8 | 42 | 48% | Fair |
Verdict combines mean daytime high with rainy-day frequency. “Rainy days” is the share of days in the month with at least 1 mm of rain.
April is the driest month, with rain on 35% of days and daytime highs near 14.6°C (58°F). December is the wettest, at 48%. The warmest month is July at 23.2°C (74°F); the coolest is January at 5.4°C (42°F).