Keep the umbrellas and raincoats handy — forecasters say Hawai'i's March weather madness will continue to the end of the month and beyond.

"We're looking for a slight improvement of the weather, but overall, it'll be wet through the weekend," National Weather Service forecaster Ray Tanaka said last night. "I can't see the pattern changing over the next seven days."

O'ahu will experience periods of rain today. "It may not be steady through the entire day," Tanaka said, "but more light to moderate with occasional thunderstorms."

Maui is expected to get most of the rainfall today.

This is the sixth straight week of heavy rainfall in Hawai'i, which the weather service says started on Feb. 19. Many spots throughout the state have received more than 20 inches of rain in that period.

The weather service says the upper-atmospheric pattern across the Pacific Ocean has been relatively stationary, with a series of upper-level storm systems forming north and west of Hawai'i since mid-February. The result has been round after round of rains and thunderstorms across the state.

Kaua'i has been hit the hardest. Mount Wai'ale'ale has had 128.8 inches of rain since Feb. 19, while the 34.77 inches at Lihu'e Airport in March is a record for any month there.

Repeated floods through the western end of the Kaua'i Marriott Resort property in recent weeks have caused significant erosion on Kalapaki Beach, turning the remaining sand a darker shade of brown.

Manager Bill Countryman said that all the hotel's normal guest services remain open, but he concedes there's less beach than there used to be.

"We're hoping that the tide will bring some of the sand back in. Our grounds manager said that should happen," he said.

The hotel has closed 25 rooms on the ground floor of the hotel's eastern wing, and the hallways of that wing are fortified with sandbags. However, Countryman said that a series of concrete barriers put in place after the first flood in mid-March appear to have worked, preventing further inundation during subsequent downpours.

In other parts of the island, Kalawai Park remained closed because of flooding at its restrooms, and parts of Lydgate Park and Kamalani Playground were closed after an electrical failure caused a sewage spill into water standing in the park Sunday.

The wet weather conditions statewide are similar to those of March 1951, says the weather service. The heavy rains and flooding of 55 years ago caused agricultural damage estimated at $1.3 million.

Reach Rod Ohira at rohira@honoluluadvertiser.com and Jan TenBruggencate at jant@honoluluadvertiser.com.