What environmental indicator suggests rain will arrive within the next 24-36 hours?

Mares' tails, which refer to cirrus clouds appearing high in the atmosphere, are a classic indication of impending rain. These clouds often signal that a change in weather is approaching, typically associated with a frontal system moving into the area. When you see these high, wispy clouds, they generally suggest that moisture in the atmosphere is increasing, which can lead to precipitation, often within a timeframe of 24 to 36 hours.

High humidity can indicate that rain is possible, but it does not specifically predict it as effectively as mares' tails. Clear skies, on the other hand, generally point to stable weather conditions, where rain is unlikely. A sudden temperature drop may occur with weather changes, but it is not a reliable indicator of rain on its own. Therefore, the presence of mares' tails is the most accurate environmental indicator of rain in the near future.