What this solves

Most trekkers come to Yading in July (because that's when they have holiday) and are surprised by a 70% probability of cloud on the Three Peaks. The tool surfaces the counter-intuitive truth: late September to mid-October has the highest probability of full summit views on Tanggu La, with a similar 2-week block in late April to mid-May as the secondary peak.

When can you actually go?

Month preference (soft — you'd prefer this)

Risk tolerance

Window length (days)

Snowline preference

How to read the result

Each week is scored on five dimensions:

Numbers are 2018-2023 averages from Daocheng county weather station (3,750 m), adjusted for the ~1,000 m altitude gain to Tanggu La using a standard lapse rate of −6.5 °C/km.

Limitations

FAQ

Q: Is it really worth waiting until October vs going in July?
A: For most. The summit-view probability at Tanggu La in October is ~75%, in July is ~25%. If you've travelled a long way and have any flexibility, October wins. If July is your only option, plan to enjoy Milk Lake + Five-Colour Lake and skip the summit.

Q: What about Christmas / New Year — is winter a no-go?
A: Generally no. Snow on the upper trail is consistent December through February. The inner kora is technically doable by experienced parties with proper gear, but the park service is reduced and rescue capacity is limited. Not recommended for first-time visitors.

Q: Why is April–May a secondary peak rather than the primary?
A: Post-monsoon (after the rains have washed the air clean) is more stable than pre-monsoon (which has occasional late-season cold fronts). But April-May has fewer crowds, lower prices, and wildflowers — a real trade-off.

Q: I'm in Daocheng for a wedding in late June — should I add a trek?
A: Yes for the day-loop, no for the inner kora. Late June still has monsoon risk and trail mud. The day-loop to Milk Lake + Five-Colour Lake is achievable if you're fit and start early.