The water quality in general in the inner Oslofjord gets a thumbs up from the municipality, but they advise against swimming for a day after heavy rain. Heavy rain is defined as more than 1 mm per hour.
Rainy weather is beyond our control, but it is natural that you want to cool down after a sauna. We have showers at Langkaia and a rinsing hose at Aker Brygge (working with a shower there too), for those who do not want to bathe when it has rained. If you still want to jump in, it is recommended to be careful with your head under water, and not swim with open wounds.
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