Hiking Weather

Altitude-aware weather forecasts for hiking routes using Open-Meteo (free, no API key).

Core Workflow

1. Determine Route Info

Most users will just say a mountain/trail name. Work with whatever they give:

Typical: user gives a mountain or trail name

Search for: coordinates, trailhead elevation, summit/highest point elevation. This is enough — no GPX needed.

Example: “Tongariro Alpine Crossing” → trailhead 1120m, summit 1868m, coords -39.135, 175.651

If user gives coordinates + elevation range, use directly.

If user provides a GPX file (advanced):

python3 scripts/parse_gpx.py <file.gpx> --max-points 8

If output shows needs_elevation_lookup: true, fill elevations:

curl -s "https://api.open-meteo.com/v1/elevation?latitude={lat1},{lat2}&longitude={lon1},{lon2}"

2. Select Pressure Levels

Map route elevations to pressure levels. See references/open-meteo-api.md for the altitude↔pressure table.

Rules:

• Always include one level BELOW route minimum and one AT or ABOVE route maximum
• For a 1100–1868m route: use 900hPa (~1000m), 850hPa (~1500m), 800hPa (~1900m)
• For a 2000–3776m route (e.g. Fuji): use 800hPa, 700hPa, 600hPa

3. Fetch Weather Data

Build the Open-Meteo API call. See references/open-meteo-api.md for full parameter reference.

Essential variables:

• Surface: temperature_2m, apparent_temperature, precipitation_probability, precipitation, snowfall, weathercode, cloudcover, cloudcover_low, cloudcover_mid, cloudcover_high, visibility, windspeed_10m, windgusts_10m, winddirection_10m, freezinglevel_height
• Per pressure level: temperature_{level}hPa, windspeed_{level}hPa, winddirection_{level}hPa, cloudcover_{level}hPa, relativehumidity_{level}hPa

Set elevation parameter to the summit elevation for accurate surface forecasts at the highest point.

4. Analyze and Present

See references/safety-thresholds.md for go/no-go criteria.

Output format (adapt to context — Telegram, Discord, etc.):

🥾 [Route Name] — [Date]
📍 [Elevation range]m

⏰ Best window: [time range]
[✅/⚠️/🔴/❌] Overall: [go/caution/risky/no-go]

Summit ([elevation]m, ~[X]hPa):
  🌡️ [temp]°C (feels [apparent]°C)
  💨 Wind [speed] km/h, gusts [gust] (direction)
  ☁️ Cloud [%]% at summit level
  👁️ Visibility [X] km
  ❄️ Freezing level: [X]m [above/below summit]
  🌧️ Precipitation: [%]% chance

Trailhead ([elevation]m):
  🌡️ [temp]°C
  💨 Wind [speed] km/h

📋 Gear notes:
  - [wind shell / warm layers / rain gear / crampons etc.]

⚠️ Alerts:
  - [any concerning conditions]

Key analysis points:

• Compare freezing level to summit elevation → ice risk
• Check cloud cover at summit pressure level → visibility/view quality
• Cloud cover below summit + clear at summit = potential cloud sea 🌊
• Wind at summit level vs surface → ridge exposure risk
• Identify best weather window (typically early morning)
• If multi-day forecast requested, recommend best day

Critical Rules

• Always use pressure level data for summit conditions, not just surface temperature_2m (which is corrected to the elevation parameter but doesn’t capture cloud/wind layering)
• State the data source and forecast time clearly
• Never say “probably fine” — use the threshold table and be specific
• If conditions are marginal, recommend early start and turnaround criteria
• For multi-day hikes, check each day and each camp elevation separately