A weather tool for pilots, paragliders, hang gliders, and atmospheric enthusiasts that computes the environmental lapse rate from the surface up to 5,000 ft MSL using real-time forecast data from Open-Meteo.
The environmental lapse rate describes how quickly temperature drops with increasing altitude. It's a direct indicator of atmospheric stability — a steep lapse rate means unstable, convective air; a shallow rate or inversion means stable, suppressed conditions.
This calculator fetches pressure-level forecast data (1000–850 hPa) for any location and computes:
- Mean lapse rate from the surface to 5,000 ft MSL
- Layer-by-layer breakdown showing the rate between each pressure level
- Stability category (Inversion → Isothermal → Normal → Conditionally Unstable → Dry Adiabatic → Superadiabatic)
- Temperature profile (sounding) from surface to 5,000 ft
- 72-hour timeline of how lapse rates evolve through the forecast period
- Multiple forecast models — compare GEFS Ensemble Mean, Best Match, and GFS HRRR side by side with colored overlays
- °F / °C toggle — all temperatures and lapse rates convert instantly; lapse rates display in °F/1000ft or °C/km
- City search or GPS coordinates — type a city name for autocomplete, or paste coordinates directly (e.g.
34.448, -119.293) - Use My Location — one-click GPS detection via the browser
- Daylight-only time slider — restricted to 8 AM–7 PM local time with day separators and clickable hour marks (8a, 10a, 12p, 2p, 4p, 6p)
- Reference table — lapse rate categories with stability descriptions
| Category | °C/km | Stability |
|---|---|---|
| Inversion | < 0 | Very stable — temperature increases with height |
| Isothermal / Weak | 0 – 3 | Stable |
| Normal | 3 – 6.5 | Standard environmental lapse rate |
| Conditionally Unstable | 6.5 – 9.8 | Unstable if saturated |
| Dry Adiabatic (DALR) | ≈ 9.8 | Neutral for unsaturated air |
| Superadiabatic | > 9.8 | Absolutely unstable |
All forecast data is fetched client-side from the Open-Meteo free public API — no backend or API key required. Temperature and geopotential height are retrieved at pressure levels 1000, 975, 950, 925, 900, 875, and 850 hPa. Lapse rate is calculated as −ΔT/Δz for each layer within the 0–5,000 ft MSL column.
- React + Vite (TypeScript)
- Recharts — lapse rate timeline and temperature profile sounding
- Tailwind CSS — dark atmospheric theme
- Open-Meteo API — forecast data and geocoding