The Nintendo Switch will have it’s online services taken down for a brief period on August 9th. The maintenance period starts at 5:50 pm Pacific Time and lasts until 7:30 pm Pacific Time.
Some network services may be temporarily unavailable during this time period. Naturally, there are not any details about what the maintenance involves or improves.
Luckily, it takes place after Splatoon 2 finishes up their latest event, Splatfest, so the game will not be interrupted.