May–Sep offers blue Andean skies; Oct–Nov shoulder season with fewer crowds; Dec–Mar beach weather but rainy highlands; Apr sees lush post-rain greenery.
January: Beach weather in Lima; heavy Andean rain, Amazon lush.
February: Warm coast; Inca Trail closed for maintenance.
March: Rain easing, blossoming Sacred Valley.
April: Green landscapes, moderate crowds.
May: Dry season starts; ideal trekking temps.
June: Peak festivals (Inti Raymi), sunny skies.
July: Clear, busy, Independence Day events.
August: Similar to Jul; crisp nights, starry Andes.
September: Tail-end dry; fewer trekkers.
October: Shoulder season; mild coast; occasional showers Andes.
November: Warmer, good Amazon wildlife spotting.
December: Start rainy; surf towns peak for summer.