Rain drops on an Euphorbia Pulcherrima

For the first time I record rain drops on the leaves of an Euphorbia Pulcherrima (聖誕花). The round rain drops stay quietly like pearls on the leaves. It is strange that they do not run down the leaves and disappear on the floor or into the pot below.

There may be several reasons for this:
1. The humidity is high, so they will not evaporate so fast and gone.
2. There is no heavy rain, otherwise these droplets will not stay longer on the leaves.
3. The leaves are strong enough to support the droplets.
4. The surface of the leaves are not smooth or slippery.