If the current weather conditions change to rain, you will get a notification.
If
Current condition changes to
This Trigger monitors changes in the current weather condition. When one of those conditions is met the Trigger fires. Currently only these simple conditions are supported: Rain, Snow, Cloudy, Clear.
Then
Send a notification from the IFTTT app
This action will send a notification to your devices from the IFTTT app.
Explore more great ways to automate Notifications and Weather Underground