The French word "meteosensible" means weather sensitivity in English.
All human activities are "weather sensitive" : heat, cold, rain, the amount of sunshine in each day,... will all have an impact on the behaviour of all human beings.
Considering this, there will not be as many visitors at Disneyland Paris, Disney World Orlando, or the Eiffel Tower if the temperature is 25°C (77°F°) or 10°C (50°F), with 3 millimeters of rainfall or 10 millimeters, or when there are blue skies versus clouds...
Traffic in most places is very weather sensitive.
This means that it is critical to take into account weather forecasts in order to calculate waiting times and crowds. Not taking it into account translates into unreliable traffic (crowd) predictions.
meteosensible.com is the most reliable and most precise site that you will find online, because it is the only site which takes into account meteorological data in calculating its predictions.