Quick answer: The best time to visit Chiang Mai is November–February (cool season; avoid March–April burning season). Expect a mid-range budget of about €35 per day. Visa: Visa-free/visa-on-arrival for many passports — check current rules.
Why this window
Chiang Mai is the classic nomad base: old-city temples, mountain air and Sunday markets. Note the burning season (Mar–Apr) — plan around it.