The best time to visit Gaoua is November to February — the cool dry season, when temperatures are pleasant during the day and the roads to outlying Lobi villages are firm. December and January are the most comfortable months.
March to May is brutally hot, with highs of 40°C and Harmattan dust from the Sahel filling the air. The rainy season (June to September) cools things down but turns the dirt tracks into mud and makes village visits much harder. October is a transitional shoulder month when the landscape is briefly green and the millet harvest is in. Check the security situation for southwest Burkina Faso before you go — the region is generally calmer than the north but conditions change.