A potted pelargonium left outside can receive more rain than expected, especially when an outer container or saucer catches the runoff. Begin by emptying collected water and checking that drainage can escape.
Inspect the stems and leaves without immediately removing large amounts of healthy growth. Wet compost does not automatically mean the plant needs an emergency root wash or a hard cut.
Find a position with drainage and airflow
Move the container away from a place where further water is being channelled into it. An overhanging roof can help with rain but may also reduce light, so consider both conditions rather than exchanging one problem for another.
Check the compost before the next watering. Do not water on the previous routine simply because the rain has stopped. A large root ball may remain wet after its top surface changes colour.
If parts of the plant soften or collapse, identify the affected tissue and investigate further. Keep a photograph of the damage and note whether it is spreading. Fertiliser is not a remedy for stems or roots struggling in a persistently wet container.
Related reading: Geranium Care: Potting, Watering and Seasonal Feeding.