Rates a walk or a hike from the weather that makes or breaks it. GoDay scores every daylight hour and finds the best 4-hour stretch of each day, long enough for a proper walk.
A thunderstorm holds the score at 2, and one due within two hours at 4. A feels-like above 38°C (100°F), rain heavier than 4 mm an hour, or gusts over 70 km/h (43 mph) hold it at 3.
Daylight counts too: at dusk the score is held at 4, and once it's dark at 2.
GoDay treats a feels-like of 10 to 28°C (50 to 82°F) as ideal. Above 32°C (90°F) it's hot work, and above 36°C (97°F) GoDay rates it dangerous.
It looks at the rain over the last 24 hours: under 2 mm the trail is likely dry, 10 to 25 mm muddy, and more than that soaked.
Most walks take a few hours, and a dry hour followed by a downpour isn't a good hike. The window averages the hours but keeps the worst gust and the heaviest rain in the score.