Spring and autumn are ideal. April–May and September–October bring daytime temperatures in the 18–25°C range, cool nights and minimal afternoon thunderstorms. The trails are clear, the cave temperatures are pleasant, and the long lava traverses are realistic.
Summer is unforgiving on the black lava — surface temperatures can exceed 60°C in mid-afternoon — and any hike on the basalt should start at dawn. July and August also bring the New Mexico monsoon, with sudden, violent thunderstorms that can flood arroyos and turn the unpaved roads to mud.
Winter is cold and beautiful. Snow occasionally dusts the lava beds, creating one of the most dramatic landscapes in the Southwest. Daytime temperatures stay above freezing most of the time but nights drop hard. Check road conditions before any winter trip — some side roads close after heavy snow.