King tides are back on the California coast. A coastal flood advisory is in effect for Orange and San Diego counties, with high tides of 7.1 to 7.6 feet expected through Tuesday 10 November, and forecasters say the highest water is expected on Sunday and Monday. The National Weather Service expects this round to be less severe than the record event in late October, mainly affecting low-lying walkways and waterfront areas.

The return of the high water comes less than two weeks after record-breaking tides flooded parts of the Southern California coast. On 26 October, the Balboa Peninsula in Newport Beach flooded under the highest tide in the city's history, and the following day the tide gauge at the Port of Los Angeles in San Pedro reached 8.2 feet, breaking a record more than a century old. In Huntington Beach, flooding damaged 114 homes and other buildings, six homes were yellow-tagged after safety inspections, and seawater flooding in Sunset Beach forced temporary closures along Pacific Coast Highway.

Cities prepare for Thanksgiving tides

Coastal cities are already preparing for worse to come. The City of Newport Beach has asked residents and property owners to take immediate precautions ahead of exceptionally high king tides expected from 23 to 27 November, 22 to 26 December and into the new year. The city says ocean water levels could rise 12 inches or more above October's record-breaking high tide of 8.4 feet, significantly increasing the risk of coastal flooding in low-lying neighbourhoods and waterfront areas, including properties that did not flood in October.

Newport Beach has received authorisation from the California Coastal Commission to issue emergency permits for seawall repairs and extensions, with streamlined plans and faster permitting, and the city council is due to hold a study session on the flooding on Tuesday 10 November. The city has already handed out more than 20,000 sandbags since the October flooding, and crews have been reinforcing protective sand berms, inspecting pumps and tide valves, and preparing flood-prone neighbourhoods.

Warm seas and El Nino behind the surge

King tides occur when the sun, moon and Earth come into near alignment, with the sun's gravitational pull adding to the moon's to produce higher tides. Forecasters say this year's tides are being supercharged by unusually warm Pacific water and an El Nino-driven Kelvin wave that has lifted local sea levels, with sea levels running more than a foot above normal before the tides arrived.

Forecasters warn that the Thanksgiving week tides, from 24 to 26 November, could reach 8.4 to 8.5 feet even without a storm, matching or beating October's records. Further king tide periods are expected around Christmas, from 23 to 25 December, and again from 21 to 22 January. A beach hazards statement is also in effect for Los Angeles and Ventura counties because of rough surf and a high risk of rip currents.