Moraine Lake in October

Peak season runs July through early September when the road is guaranteed open and weather is warmest. July and August see daytime highs around 20°C (68°F) but also the biggest crowds – that 6 AM parking situation is real. September offers fewer people and stunning fall colors, though mornings can dip below freezing. June works if you don't mind cooler weather and possible road closures from late snow. The lake often stays partially frozen until mid-June. October can be magical with fresh snow on the peaks, but the road typically closes by mid-month. Weather changes fast in the mountains – pack layers even in summer. Afternoon thunderstorms happen regularly in July and August.