May and June are the best months — the Loire Valley is green, the weather is warm without being oppressive, and the crowds are manageable. The gardens at Clos Lucé and Chanteloup are at their best.
July and August are the peak season. The chateau gets busy by midmorning; arrive at opening (9 am) or after 5 pm when day-trippers from Tours have gone. The Son et Lumière (sound and light show) at the chateau runs on summer evenings — good in warm weather, excellent in a thunderstorm.
September and October offer warm days, thinner crowds, and Loire wine harvest. The vendanges (grape harvest) along the Vouvray and Montlouis appellations east and west of Amboise make this a particularly good time for wine enthusiasts.
Winter (November–March) is quiet but the chateau and Clos Lucé stay open year-round. Amboise at Christmas has a small market; the candlelit evening tours at the chateau in December are genuinely atmospheric.