Games : How do rainy days affect plant growth?

You can water your plants twice a day, this increases how quickly they'll grow. On rainy days, your plants are watered for you (by the rain, obviously).

I remember that, in Tale of Two Towns, weather could change midday. If it rained in the morning or in the afternoon, you could get credit for two waterings. But if it rained the entire day, you'd only get credit for one watering.

Story of Seasons, on the other hand, has a "one weather all day" system. How does this affect plant growth? Do you get credit for two waterings on rainy days or just one?