Can I fly?

I wanted one look that answers “is it worth driving to the field this afternoon, with this model?”. Each aircraft has its own limits — a 5″ quad shrugs off wind that grounds a foam trainer, and a car only cares about rain — so you set them once and the page colours the next two days (or the week) hour by hour.

It is a weather tool, not an airspace one. It knows nothing about where you are allowed to fly, airports, restrictions or permissions. Check those with your country’s own service — in the UK Drone Safe, in the US B4UFLY, in the EU your national authority’s map — and look at the trees before you launch.

How to use it

Add a field. Use my location (the browser asks), or type coordinates (51.5072, -0.1276 or 51.5072N 0.1276W) and Add field. Keep as many as you like and pick one from the list. Give a runway or strip heading (either end; 27 is 270) and the crosswind is part of the judgement, for whichever end faces into wind.
Pick an aircraft. The examples — 5″ FPV quad, GPS camera drone, foam trainer, thermal glider, RC car — are starting points. Under Edit limits set the maximum wind, gusts, wind at 120 m, crosswind, rain (mm/h), chance of rain, the minimum visibility and cloud base, the temperature range, the highest Kp, and whether it flies only with the sun up or until civil dusk. Empty boxes aren’t checked. An hour turns amber when a value passes 80 % of a limit (you can change that). Copy as new makes your own profile.
Read the timeline. One row per day, one square per hour, in the field’s own time zone: green go, amber marginal, red no; dark hours have a shaded foot, and the best window is outlined. Tap an hour for its numbers and the reasons. Best windows lists the longest runs of green (tick Count amber hours to include marginal ones), calmest first among equal lengths.
Switch the speed unit (km/h, mph, knots, m/s) and the span (48 hours or 7 days) at the top.

Where the numbers come from

Forecast: Open-Meteo, which picks the best weather model for the place. Gusts are only forecast at 10 m; the 80 m and 120 m figures are mean wind. Visibility isn’t in every model, and an hour without it isn’t marked down for it.
Cloud base is an estimate from the spread between temperature and dew point (about 125 m per °C), good for convective cloud and rough otherwise.
Kp: the observed and forecast planetary K index from the NOAA Space Weather Prediction Center, in three-hour blocks for about three days. In a geomagnetic storm (Kp 5 and up, G1) GPS positions wander and some drones won’t arm. Hours beyond the Kp forecast aren’t judged on Kp.
Sunrise, sunset and civil twilight are worked out on the page (NOAA’s solar formulas). For golden hour, the moon and other dates, see sun and moon.

For runway wind components on a real aerodrome report, aviation weather decodes METARs and TAFs, and the E6B has the wind triangle.

Privacy

The page sends the chosen field’s latitude and longitude (rounded to four decimals, about 10 m) to api.open-meteo.com to get the forecast, and fetches the Kp index from services.swpc.noaa.gov, which sends nothing about you beyond the request itself. Your location is only asked for when you press Use my location, and stays in the page. Fields and aircraft profiles are kept in this browser’s local storage.