Imilchil is a high-altitude village and the seasons matter. From November to April the plateau is often under snow, the unpaved approach roads can be impassable, and night-time temperatures fall well below freezing. Many auberges close in winter.
The best window is May to early October, when the days are warm, the lakes are full from the spring melt, and the high pastures are green. Bring warm clothes anyway — even in August, dawn at 2,200 metres is cold.
The big draw is the Moussem des Fiançailles in late August or September. Dates are fixed locally and shift from year to year; ask in advance, because accommodation is overrun during the festival and you need to plan ahead. Saturday is market day — make sure your visit includes one.