Puget Sound, April 2026
The surface of central Puget Sound off Jefferson Head was 9.7°C in April 2026. The April average since 2000 is 9.5°C, with the warmest April at 11.6°C in 2005 and the coolest at 7.9°C in 2023. King County publishes its marine samples after review, about six months behind, so this is the newest month there is.
Oxygen in the deep water. At 180 metres and below, the water held 7.3 milligrams of oxygen per litre in April 2026, and 6.5 on average over the last twelve months. The low point usually comes in early autumn, when dense, oxygen-poor ocean water that has crept in along the bottom over the summer has reached furthest; the lowest month in this record was 5.2, in November 2014. That is not hypoxia, the level below about 2 milligrams at which fish leave or die: the main basin is well flushed. Hood Canal and the south Sound are where Puget Sound runs short of oxygen.
Sea level. At the Seattle tide gauge on Colman Dock, the water stood 136 millimetres above the 1983-2001 average in September 2026. The 12-month mean is +118 mm. The record runs back to 1899, and its first 12-month mean, to November 1899, was -210 mm: the last year stood about 33 centimetres higher than the first. This is relative sea level — the water against the land the gauge stands on — and a single month is full of weather: low pressure and south winds stand water up in Elliott Bay every winter, and El Niño years run high. The 12-month line is the one to read.
Source: King County Water and Land Resources Division, marine water quality data, station KSBP01; NOAA tide gauge 9447130, monthly means. Auto-generated each build.