King Tide season starts this week. When to expect the highest high tide of the month

JACKSONVILLE, FLA – It’s that time during the start of fall when the highest tides of the year impact our area.

King tides are the extreme high tides that occur when the gravitational forces of the sun and moon align, resulting in the highest possible tides of the year.

Fall is prime time for these astronomical events in our region, with late September through November delivering the most pronounced tidal swings. These amplify flooding risk in low-lying areas—especially in coastal zones and the St. Johns.

Contributing Factors: Harvest Moon + Incoming Nor’easter

This year’s Harvest Moon, rising closest to the autumnal equinox, adds extra lunar gravitational pull, supercharging tidal peaks. It will coincide with a developing nor’easter that is pushing water into the river from the onshore flow, resulting in tidally trapped water that I discussed last week.

Know Your High Tide Times: Be aware of when high tide is for your specific area so you know when to expect the highest water levels.

• Week of September 11: Expected to bring the highest high tide of the month, reaching 6.57 feet above mean sea level (MSL) by 11:30 Thursday morning at the beaches.
• Early October: The first full week continues the trend of high tide swings with frequent marsh inundation. Tides will reach 7 feet above MSL on October 8-9.
• November 6: Notably, this is predicted to be the highest astronomical tide of the year at 7.19 feet above MSL at Jacksonville Beach. Expect substantial tidal flooding in vulnerable spots if rainfall or storm surge coincide.