Use OpenWeatherMap data to compile historical cloud cover by hour in specific months to figure out when the best time of day is to reserve VFR flight lessons.

cloudCover.js

data
.filter(x => (new Date(x.dt_iso)).getMonth() > 5 && (new Date(x.dt_iso)).getMonth() < 8)
.reduce((acc, x) => { 
  const h = (new Date(x.dt_iso)).getHours(); 
  return acc.hasOwnProperty(h) ? 
  Object.assign({}, acc, { [h]: acc[h] + x.clouds.all }) : 
  Object.assign({}, acc, { [h]: x.clouds.all }) 
}, {});