Beach-goers around Puget Sound will be combing through seaweed, starfish, and shells this weekend during low tide.

In the Seattle and Tacoma areas, this year's lowest tide hit Friday at -3.7 feet at 12:42 p.m., according to the National Oceanic and Atmospheric Association. Extreme low tides continue through the weekend, allowing for good beach exploration.

A combination of factors causes tides to be lower than normal right now: a perigean tide is occurring, we’re close to the summer solstice, and weather patterns are changing.

Perigean tides happen when the moon is either new or full and closest to the Earth, causing greater tide swings. Tides also tend to be higher or lower than normal leading up to and after the summer solstice on June 21, due to the position of the sun and the equator, according to NOAA.

Tides are measured relative to the mean sea level and are caused by the gravitational pull of the sun and the moon.

TIDE TABLES: Seattle | Tacoma | Everett (via NOAA)

Extreme low tides over the weekend are expected to measure -3.3 feet on Saturday at 1:30 p.m. and -2.5 feet Sunday at 2:20 p.m. in Seattle.

While they won’t be the lowest of the year, tides in the Everett area are also noteworthy. They are expected to measure -3.4 feet Thursday and Friday at 12:02 p.m. and 12:48 p.m., respectively. They will be -3.0 feet Saturday at 1:36 p.m. and -2.1 feet Sunday at 2:25 p.m.

More extreme low tides are expected in mid-July measuring around -3.5 feet in Puget Sound.