The actual fascination
The Met Office describes how oils associated with dry ground can be released into the air as moisture conditions change around rain. Petrichor is the familiar name for the earthy smell associated with rain on dry ground. It is not a personal weather forecast.
Describe before you diagnose
Earthy, leafy, dusty and fresh are useful notes. Do not force every smell into the same label. Record the setting too: a garden path, a paved street and a plant pot are different places, even when the weather is similar.
The dry-to-wet notebook
At a safe sheltered place, note whether the ground was dry, whether rain has begun and what you notice. Repeat another day if you want. You are building your own record, not proving that every person smells the same thing.
A pleasingly low-tech project
Use a notebook you already own. Leave unfamiliar plants and substances alone. If the weather becomes unsafe, the fascinating thing can wait. The point is to notice an ordinary event more carefully, not to chase a storm.
Your small mission
Describe a rainy-day setting in one sentence, then add one question.
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