Gov. Josh Green on Monday — the 78th anniversary of a devastating tsunami in Hilo — proclaimed April as Tsunami Awareness Month in Hawaii.

At a news conference held alongside emergency management officials, Green warned that tsunamis are unpredictable, potentially devastating disasters that can occur any time year-round.

“It is imperative to know what to do to protect lives and property from tsunamis,” he said in a statement. “Being aware, educated and ready to take action will save lives.”

On April 1, 1946, an 8.6-magnitude earthquake occurred off the Aleutian Islands of Alaska, generating tsunami waves that would reach the Hawaiian islands about 4-1/2 hours later.

There was no tsunami warning system at the time, and the waves obliterated Hilo’s waterfront, killing 158 people statewide, according to the National Oceanic and Atmospheric Administration.

By 6:30 a.m. that day, waves reached 53 feet on Hawaii island, according to International Tsunami Information Center Director Laura Kong. They reached 33 feet on Maui, 35 feet on Oahu, and 45 feet on Kauai.

Today, the Pacific Tsunami Warning Center monitors for potential tsunamis throughout the Pacific Ring of Fire (areas with active volcanoes and frequent earthquakes), 24 hours a day, 7 days a week throughout the year.

“Hawaii is a bullseye for distant tsunamis from around the Pacific Ring of Fire,” said Kong.

Hilo tsunami survivor Jeannie Johnston shared her memories of surviving the disaster in 1946.

She was 6 years old at the time, living with her grandparents in Keaukaha, just outside of Hilo. She and her 4-year-old brother were getting ready for school when they heard car horns honking.

They looked outside, and saw water rising to the same level as their clothesline, 5 feet up, submerging cars.

With their uncle, they ran up into a jungle in bare feet, and camped out at a radio tower for several hours. Fortunately, they survived, but others did not.

“So please be prepared,” said Johnston. “Get your family, and make a family plan. Make sure everybody knows where to go and what to do in case of different disasters.”

Tsunamis are giant waves generated by earthquakes, volcanic eruptions under the sea, or other events that forcibly move large amounts of water.

In 1960, a tsunami generated by an earthquake off of Chile hit Hilo, causing 61 deaths, according to NOAA.

Although some are caused by earthquakes hundreds of miles away, which take hours to reach the state, an earthquake within Hawaii could generate a tsunami within minutes.

Officials said residents should prepare by knowing whether they live or work in a Tsunami Evacuation Zone.

They should know their evacuation routes, have a family plan in place, and pack a “go bag” of essential items for emergency situations.

Tsunamis generated in recent years in the Ring of Fire — from Tonga to Japan — have left vast devastation in their wakes, according to PTWC Director Charles McCreary.

“Another destructive tsunami will strike the state of Hawaii,” he said. “We just don’t know when, so having this Tsunami Awareness Month every year is what helps us be prepared for the next tsunami, both now and in the future.”

In the open ocean, tsunami waves can travel up to 800 kilometers per hour, as fast as a jet plane, according to NOAA. Although tsunami waves may be small in the open ocean, wave heights can increase substantially as they approach the shore.

More information on Hawaii tsunamis is available at hawaiitsunami.org.

PREPARING FOR A TSUNAMI

>> Double-check if you live, work, play or travel in a tsunami evacuation zone, extreme tsunami evacuation zone or in a safe zone.

>> Study tsunami evacuation information and maps online at honolulu.gov/dem (click on Tsunami).

>> Prepare a go bag of essential items to take during an emergency.

>> When an evacuation is necessary, sirens will sound and significant, widespread land flooding is expected. Stay away from rivers, streams and any water channels leading to the ocean.

>> A Tsunami Watch means you should prepare and be ready to act because a tsunami may occur.

>> A Tsunami Advisory means you should move away from beaches and low-lying coastal areas and evacuate habors and marinas.

>> A Tsunami Warming means move to high ground or inland. Quickly leave red Tsunami Evacuation Zones to Green Safe Zones as indicated on the Tsunami Evacuation Map. In Honolulu, this could be the 4th floor or higher of a building 10 stories or taller.

>> If you observe warning signs from nature, i.e. feel a strong earthquake, see a sudden rise or fall of the ocean, move to higher ground immediately.

Visit ready.hawaii.gov for more on preparing for tsunamis and other hazards.