Here's why:
* Common Sense: The phrase simply reflects a practical consideration: outdoor activities are often contingent on the weather.
* Flexibility: It can be applied to various scenarios, from playing outside with kids to attending a picnic or a sporting event.
* No Historical References: There are no readily available sources that attribute the phrase to a specific person, time period, or event.
Origin Possibilities:
* Folklore: It's possible the phrase originated in rural areas where weather conditions were more crucial for daily life and work.
* Informal Speech: It might have evolved organically from casual conversations and became a part of common parlance.
While its exact origins might remain unclear, the phrase "all day unless it rains" remains a relatable expression that embodies the uncertainty and potential for change brought on by weather.