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Honolulu Climate / Enviroment

The climate in Honolulu is moderate with very little change throughout the year. In contrast to the mainland United States, Honolulu does not observe daylight savings time and does not have four seasons. Instead, residents of Honolulu consider the year as divided between the dry season, which runs from April to October, and the rainy season, which runs from November to March.

The average highs range between 80 degrees and 90 degrees in this tropical paradise, with the average lows ranging between 65 degrees and 75 degrees. The humidity ranges between 67 percent and 81 percent in the morning and 52 percent and 61 percent in the afternoon. You can also enjoy tropical breezes that blow at an average of 11 miles per hour. When you are ready to play in the ocean, you’ll be greeted by water that is between 77 degrees and 82 degrees.

Each year, Honolulu has 270 sunny days and 98 wet days. But before you decide to leave your umbrella at home, here is a little tip. Where you are in the city will dictate the likelihood of seeing raindrops. If you are at Waikiki, downtown Honolulu or on the western side of the city, where the weather is hot and dry, chances are you’ll have sunny skies. But travel to the eastern side of the city and the hills, where the weather is cooler and moist, and you are more likely to see passing clouds and brief showers.

Seasons

Since Hawaii lies at the edge of a tropical zone, it technically only has two seasons. Both seasons are warm, though some weather-related problems persist even in this close-to-ideal climate.

With the dry season, from April to October, come hundreds of brush fires. The Honolulu Fire Department recommends that you clear brush 30 to 100 feet around your house, remove all flammable items from around your house, and make sure there is clear access to your house.

But the rainy season, from November to March, brings its own problems. Although rain rarely lasts for more than three days, heavy rains can cause mudslides and force some creatures in Hawaii out of their natural habitat. For example, when rain churns the ocean, expect to see an increase in shark activity. On land, you can expect to see an increase in centipedes. Be careful moving them because they pack a big bite. Bufo Toads are poisonous and life threatening, and also are seen more often in rainy weather. Keep children and pets away from these creatures. An increase in Geckos and ants can also be annoying, though these creatures are not as dangerous.

Severe Weather

Although you are living in a tropical paradise, you should always be aware of the potential for severe weather. Thunder storms, hurricanes and tropical storms, tornadoes, volcanic eruptions, earthquakes, tsunamis and drought are all weather hazards you should be prepared to navigate – even if most of these are extremely rare occurrences in Honolulu. Since being prepared means knowing the forecast, these Web sites will provide you with your local forecast information and contacts in case of an emergency.

Severe Weather Forecasts

Severe Weather Emergency Assistance

Tsunami

A tsunami is generated by underwater earthquakes. The waves of the tsunami can continue for several hours and are capable of causing destruction on the entire coastline of Oahu. However, such occurrences are quite rare; a serious tsunami has not hit Hawaii since 1975.

Signs that a tsunami is imminent:

  • Earthquake affecting Oahu: If you are in a tsunami zone, move immediately but safely to higher ground.
  • Earthquake in Hawaiian Waters: The Pacific Tsunami Warning Center (PTWC) will issue an urgent warning for the areas that could be affected. This warning will be announced over the Emergency Broadcast System via the radio and the Civil Defense sirens will be activated.
  • Distant earthquake: The Pacific Tsunami Warning Center (PTWC) will issue a Tsunami Watch until it has been confirmed or discounted. In the event that the tsunami is confirmed the PTWC will issue a warning for the areas that could be affected. This warning will be announced over the Emergency Broadcast System via the radio and the Civil Defense sirens will be activated.

If you are seeking shelter from a Tsunami, go to a steel or concrete building that has more than six floors. Make sure you are on or above the third floor. If you are outside the Tsunami Evacuation Zone, you should be safe.

Earthquakes

Thousands of earthquakes occur in the Hawaiian Islands each year. Most of these earthquakes are so small they can only be detected by instruments. The Last major earthquake was on the island of Hawaii in October 2006. It was felt on the island of Oahu and knocked the power out for the day.

During an earthquake, the earth moves in a similar manner to the deck of a moving ship. This movement of the ground itself seldom results in injury or death. Instead, most earthquake injuries and deaths are attributable to building collapse, falling objects and shattering glass.

If you feel an earthquake that is strong enough that it makes you grab onto something to remain upright and you are located in a tsunami area, move to high ground immediately. A locally generated tsunami will not give you any warning.

To be ready for an earthquake, you should check your house for any potential hazards at least once a year, including:

  • Faulty electrical wiring
  • Leaky gas
  • Inflexible connections
  • Bolt down water heaters and gas appliances
  • Make sure you know how to shut off your utilities manually
  • Securely fasten shelves
  • Anchor top heavy objects
  • Check for cracks in your ceilings and foundation

 

During an earthquake, you should remain calm. Stay inside if you are inside and stay outside if you are outside. Injuries can occur when you try to enter or exit a building. If you are inside, take cover under a heavy desk or table alongside an inside wall. Stay away from glass and don’t use matches or an open flame because of possible gas leaks. It is important to always have a fire extinguisher on hand.

If you are in a car, pull over quickly and safely but do not stop under a bridge or overpass. Stay in your car. Watch for fallen objects, downed electric wires or blocked roadways. And be prepared for aftershocks.

Thunderstorms

Thunderstorms rarely occur in Hawaii. In fact, Honolulu averages only seven weak thunderstorms a year. That’s partly because the Hawaiian Islands rarely experience a day above 90 degrees. The ocean waters are always warm at the islands’ sub-tropical location, and the atmosphere above them is mild to a height of several miles. Since thunderstorms require a thermally unstable atmosphere, they rarely form in Hawaii.

Hurricanes and Tropical Storms

Hurricanes are powerful storms that form over tropical waters, usually between June and December. The effects of hurricanes can include damaging surf and storm surges along the coastline, destructive winds, water spouts, tornadoes, heavy rain and flooding. To be classified as a hurricane, a storm must have sustained winds of 74 miles per hour or more. A tropical storm will have winds between 39 and 73 miles per hour.

During the last 50 years, three hurricanes have hit the Hawaiian Islands. Fortunately, Honolulu did not take a direct hit from any of the storms. It is important to note that if Honolulu were to take a direct hit from even a weak tropical storm, however, the effects would be devastating. The rain from the storm would be focused on the mountain slopes which would result in flash floods and landslides. Rapidly rising water levels from storm tides and high wind waves would inundate the coastal areas, erode beaches, and pound waterfront structures, highways, and other facilities. The best way, then, to prepare for a major hurricane is to make plans on how you will evacuate the island if such an event were to occur.

It is essential to know the difference between a hurricane/tropical storm watch and a hurricane/tropical storm warning. When a watch is issued, it means that storm conditions are likely to occur on Oahu within 48 hours. You should begin preliminary precautions. If a warning is issued, it means that the threat of storm conditions is stronger, and the storm is expected to hit Oahu within 36 hours. You should take action to protect your life and property immediately. No area on the island is safe from the effects of a hurricane or tropical storm, so it is essential that everyone has emergency evacuation plans and assembles a survival kit. The Web site, www.co.honolulu.hi.us/dem/brochures.htm provides extensive information about preparing for a storm.

It is also important to stay tuned to local radio and TV stations for emergency updates, school closures, employee releases and shelter opening schedules. You can also expect sirens sounding and evacuation orders. If you are in or near a Tsunami Evacuation Zone, along ridge lines, in areas subject to flooding, or you are in a wooden-frame or lightly constructed building, you should evacuate before the winds reach 40 miles per hour. Multi-story buildings made of heavy concrete and steel and that are at least 300 feet inland from the shoreline serve as public shelters. People in these buildings should go to the third floor or above to an enclosed room, hallway or stairwell that has load-bearing walls. Evacuation maps are located in the white pages of your phone book or by going to www.oahuDEM.org.

To be prepared for a hurricane or tropical storm, make sure you are educated about how a hurricane can affect you and your family. A disaster plan is essential. This plan should consist of a secondary meeting place for your family and designating an off-island contact. You should also have a disaster kit that contains enough supplies for five to seven days. The disaster kit should include:

  • Water – one gallon of water per person per day.
  • Food – non-perishable foods that do not require cooking.
  • Utensils – don’t forget the manual can opener.
  • Light – a flashlight or portable florescent light.
  • Spare batteries – make sure you check these annually.
  • First Aid Kit – also consider taking a certified first aid course.
  • Whistle – is important for signaling for help. The sound carries farther than the human voice and it takes less energy than yelling.
  • Dust mask – filters contaminated air.
  • Sanitation – moist wipes and garbage bag.
  • Tools – wrench or pliers to turn off utilities and duct tape.
  • Maps – local area maps.
  • Prescriptions – special medications and glasses.
  • Baby items – infant formula and diapers.
  • Pets – pet food and extra water for the pet.
  • Radio – battery operated.

Helpful Hurricane Season Web sites:

Tornadoes

The Hawaiian Islands rarely experience tornadoes. There have been 40 confirmed tornados since 1950. None of these tornadoes exceeded F2 intensity and none of them caused any loss of life. Even though they are rare, they are a possibility, so you should be aware of tornado warnings and watches. The Web sites listed above for weather forecasts are a good source of information on tornadoes.

Volcanic Eruptions

Since Honolulu is more than 2,500 miles away from the U.S. mainland, it has a natural advantage when it comes to air quality. However, there is one threat to the air quality – volcanic activity at the Kilauea crater. On the Big Island of Hawaii, Kilauea is the youngest and most southeastern volcano. In Hawaiian, Kilauea means “spewing” or “much spreading.” It has been continuously erupting since January 3, 1983.

Local legend has it that this volcano is the home of the Goddess Pele and it erupts when she is angry. These beliefs are included in tribal chants sung by native Hawaiians. The scientific explanation for the eruptions is that they are caused by numerous small earthquakes within the volcano. The Hawaii Volcano Observatory, www.hvo.wr.usgs.gov, monitors the activity of this volcano.

The danger to air quality in Honolulu is “vog” or otherwise known as volcanic smog. This is only a danger when the winds are out of the south or southeast. Vog is a visible haze that occurs when sulfur dioxide and other gases emitted from the volcano chemically interact with sunlight, oxygen, moisture and dust. Vog has health, environmental and economic impacts. It can cause headaches, watery eyes, sore throats, flulike symptoms, a lack of energy and breathing problems. For people with asthma or other respiratory problems, it can be even more serious, tightening airways and making it difficult to breathe. The solution to vog is to stay indoors with the doors closed and the air conditioning units on. Unfortunately, the Hawaiian Islands are normally cooled by the trade winds so many buildings don’t have air conditioning units.

Local farms also feel the effect of vog. The plants get burned and the sulfur dioxide in the rain destroys fences and gates. Vog also impedes grass growth which in turn causes stillbirths in ranch animals. As a result, farmers are relocating to the mainland, changing professions, or have changed their crops to ones that do better in vog.

Drought

Honolulu gets up to fifteen inches of rain per year. Because of the increasing population, however, water management is necessary for the planning of future water needs. The following conservations measures are recommended for Honolulu residents.

  • Indoor water conservation includes: fix leaks in toilets, pipes, faucets and other fixtures, take shorter showers, shut off your water pipe if you will be away for long periods of time, turn the water off when brushing your teeth and use a dishpan with soapy water to wash dishes, then rinse with clean water quickly.
  • Outdoor water conservation includes: limit grassy areas when landscaping your yard, group plants according to their water needs and water appropriately, use soil with organic matter when landscaping, replace grassy areas with mulched areas, use plants that require little water, water your lawns two to three times a week before 9 a.m. or after 5 p.m. and use a rain barrel.

Here are a few Web sites that will help you stay on top of the drought conditions:

Plants and Animals

Hawaii is considered to be the endangered species capital of the world. Hawaii has a shocking 316 endangered species from various ecosystems. The Oahu Forest National Wildlife Refuge stands guard over some of the last remaining intact native forest. At least nine native communities can be found at this refuge. The communities include lowland mesic forests, rainforest communities, high elevation cloud forest and freshwater streams.

Here are a few Web sites that will help you get to know the plants and animals that are native to Hawaii:

Gardening in Honolulu

When planting a garden of vegetables or flowers in Honolulu, you need to take into consideration the vog. Check with your local gardening center for suggestions for the heartiest plants. The best way to garden is to follow the Xeriscaping principles. Xeriscaping is based on seven principles to plan, plant and maintain a garden that makes the most efficient use of irrigation by taking advantage of native climate conditions. Here are the seven principles:

  • Planning and design allows you to plant your garden in phases, which cuts down on your start-up costs.
  • Limit and separate turf areas; Grassy areas require more water so separate the grass from trees, shrubs and flowering plants so that they can be watered separately. Replace ground cover with low-water plants or mulch.
  • Strategically plan and place your sprinkler system; Group garden plants according to water needs. Grass is best watered with sprinklers. Trees, shrubs and garden flowers are best watered with a low volume drip or spray.
  • Use the correct soil; Add grading and soil amendments that have organic matter to provide beneficial nutrients to the plants. This will encourage your plants to take root and flourish.
  • Mulch is an ideal replacement for grass; Mulch covers and cools the soil, minimizes evaporation and reduces weed growth and slow erosion.
  • Use “Less Thirsty” plants; Use plants that are native to the island so they will thrive in natural rainfall.
  • Maintain your garden on a regular basis, which preserves the beauty of your garden and saves water.