What to look for in nature in Hawaii this April

Late April and early May is the usual answer. The Kōlea Count, a community project run with Hawaiʻi Audubon, treats April and May as the departure period and asks the public to report where the plovers gather before they go. Its guidelines give no single day, because the flocks do not leave all at once, and a bird on your lawn on April 30 may be gone by the first week of May. By then the birds have molted into the black-faced, white-edged breeding plumage.

The trip is long. The U.S. Geological Survey summary of the first radio-tracking study, which tagged plovers on their Hawaii wintering grounds in 1996 and found them again in Alaska, speaks of overwater flights of 4,000 kilometers or more. The Kōlea Count asks for arrival reports from July 1 through November 30, so the birds come back over several months. If one of your regulars vanishes this month, that is why.

If you kept a photo log in March, this is the month it pays off: compare the first picture with the last. The Hawaii March page follows the same birds through the color change.

Nesting. Hawaii’s honeycreepers do not wait for a warm spring, because their food does not follow a northern calendar. A U.S. Geological Survey study of the ʻākohekohe, or crested honeycreeper, in the Hanawī reserve on East Maui found a nesting season that ran from November to early June, so April sits well inside it. The same agency’s work on this species adds that ʻōhiʻa lehua trees flower all year with a peak in January, and that the timing of ʻākohekohe breeding tracked the abundance of ʻōhiʻa bloom. In short, the birds are busy with eggs and chicks while the trees are still well supplied with nectar. Those studies come from one species on one island, so treat the exact months as a guide for other honeycreepers rather than a rule.

You do not need a rare bird to feel it. The National Park Service calls the ʻapapane the most abundant honeycreeper and says it ranges widely in search of local patches of ʻōhiʻa bloom. At Kīpuka Kī in Hawaiʻi Volcanoes National Park, a park recording made before sunrise on a May morning in 2015 caught the forest going from silence to full song within minutes, led by dozens of ʻapapane. The ʻiʻiwi, the park says, usually stays above about 4,500 feet, where the mosquitoes that carry avian malaria and pox are fewer.

Keep your hour’s bird list in a Naturalist’s Field Journal, and walking the same trail monthly fills its same place twice pages.

Possibly the first of them. According to the state wildlife division, the Hawaiian stilt (aeʻo) breeds from March until August, busiest in May and June, and eggs hatch about 24 days after they are laid. A pair that starts in March can therefore have chicks by April, though the busiest weeks are still ahead. The state describes a clutch of three or four eggs laid on freshly exposed mudflats, and says the young are precocial, which means they are up and feeding within hours, and they stay dependent on their parents for several months. Both parents incubate and brood, and they defend the nest with loud calls and a broken-wing act.

DLNR names the places to look: Kahuku Point at James Campbell National Wildlife Refuge, the oyster ponds and the Nuʻupia ponds on Oʻahu, the river valleys at Hanalei and Wailua on Kauaʻi, and the Kanahā and Keālia wetlands on Maui. Keālia Pond National Wildlife Refuge, between Kīhei and Māʻalaea, is about 700 acres and the refuge calls it the largest lowland wetland left on Maui. It was established in 1992 for the stilt and for the Hawaiian coot (ʻalae keʻokeʻo).

The humpbacks are finishing up. The sanctuary’s boating guide gives the season as generally November through May, peaking January through March, while its about page says November through April, so the end date depends on which page you read. April is therefore a month of stragglers. The rules stay the same as the numbers fall: a boat may not come nearer than 100 yards to a humpback, and inside 400 yards the sanctuary recommends no more than six knots. If you hit or find an injured whale, NOAA’s hotline, 888-256-9840, or VHF channel 16 will reach responders.

Green sea turtles, or honu, are a different story. The state’s Division of Aquatic Resources says nesting runs from late May to early October and that about 96 percent of the population nests at French Frigate Shoals in the Northwestern Hawaiian Islands so nesting on a main-island beach is uncommon. April is mostly about basking. The state calls the Hawaiian green the only sea turtle that regularly hauls out to rest on the beach.

DLNR says so, and it issues the same reminder every April. Its April 17, 2026 release headlined the peak and repeated the guidance: monk seals pup in every month, but March through August is when most pups are born, and a mother nurses for five to seven weeks. In the state’s April 2, 2025 release, the main islands had counted three pups so far that year after 34 in 2024. NOAA Fisheries puts the species at about 1,600 seals, with roughly 400 in the main islands, and says the population has been increasing since 2013.

The distances are 150 feet from any mother with a pup, on land or in the water, and 50 feet from any other seal. DLNR also asks you to stay behind signs, cones and barriers, to keep dogs leashed and well back, and to avoid swimming near a mother and pup. A protective mother can be aggressive.

The March page covers the first weeks of the season on the Hawaii March page; April is when the beach rope and sign crews are most likely to be out.

Because the Northern Hemisphere’s plants have not started their summer drawdown. The Mauna Loa carbon dioxide record, started by C. David Keeling of the Scripps Institution of Oceanography in March 1958, is the longest direct record of carbon dioxide in the atmosphere. NOAA’s Mauna Loa Observatory sits near the summit at 3,400 meters, a spot Keeling chose in 1957 because the air there represents a large region. According to NOAA’s Climate.gov, the seasonal wiggle is driven by Northern Hemisphere summer vegetation growth, which pulls carbon dioxide down, and winter decay, which sends it back up. At Mauna Loa the highest monthly value each year occurs in May.

The table shows the monthly means NOAA’s Global Monitoring Laboratory publishes for April, May and September in recent years, in parts per million of dry air. In each year shown, May is the highest of the three and September is lower than April.

The current figure is posted on the NOAA trends page, which in early October 2026 listed August as the latest month.

Because of April 1, 1946. A great earthquake near Alaska’s Aleutian Islands sent a tsunami across the Pacific that killed more than 150 people in Hawaii and badly damaged Hilo. Accounts differ on the exact toll. The article adds that the state’s siren system was set up after that event, and Hawaii observes every April as Tsunami Awareness Month. The Hawaiʻi Emergency Management Agency says sirens normally sound on the first business day of each month at 11:45 a.m., a steady tone lasting one minute. April 1, 2027 is a Thursday, so expect the test then. If a siren sounds at any other time, the agency’s advice is to turn on a radio or television, or watch for a cellular alert, and follow the official instructions.

The Red Cross advice quoted in the 2025 news report was to learn your tsunami zone, pack a go-bag, and stock two weeks of food and water if you shelter in place. Hawaii County, Maui County, Honolulu and Kauaʻi each run their own emergency agency, and the same agency can tell you whether a siren in your neighborhood is working.

Find the evacuation zone for your hotel or campsite before you need it, and ask your county agency if you are unsure.

Yes, by the usual definition. The Western Regional Climate Center says Hawaii’s winter season runs October through April and the summer season May through September, and that below 2,000 feet the winter is the wettest time except on the Kona coast. April is a transition month, with below-average rainfall in dry areas and continued winter-style rain on windward slopes. The center puts trade-wind frequency at 50 to 80 percent in winter and 80 to 95 percent in summer, so the winds are steadying but not yet at summer strength.

The table gives NOAA’s 1991 to 2020 April normals for eight stations. Compared with March, the leeward airports are drier and the windward side is still wet: Hilo averages 9.40 inches, with 17.2 days of at least 0.1 inch, while Keāhole, on the other side of the same island, averages 0.63 inch on 1.5 days. At 11,000 feet on Mauna Loa the normal April low is 36.5 °F, and nights at or below freezing average 3.6 for the month. For forecasts and how to read a satellite picture, see our weather guide and the cloud guide.

The Climate Prediction Center posts its three-month outlooks on its 90-day outlook page, near the middle of each month. This guide does not state what an outlook says.

About 33 minutes across the month in Honolulu, and between 30 and 34 minutes at the seven towns in the table. In the Naval Observatory’s Honolulu table, April 1 runs from a 6:24 a.m. sunrise to a 6:46 p.m. sunset, and April 30 from 6:01 a.m. to 6:56 p.m. Most of the gain comes at the morning end, since the sun comes up 23 minutes earlier over the month but sets only 10 minutes later. Other towns are on the day-length page.

Because the islands keep the same time all year, the sunrise and sunset columns move smoothly, and since March 14 the mainland has been an hour closer: New York is six hours ahead of Honolulu and California three, until the first Sunday of November. The northern towns gain a little more than the southern ones, which is why Līhuʻe ends the month with a longer day than Hilo.

Every time below is Hawaii Standard Time, and Hawaii never changes its clocks. The darkest evenings of the month come in the first week, around the new moon on the afternoon of Tuesday, April 6. Two bright planets, Jupiter and Mars, stand in the evening sky in or near Leo, Venus rises ahead of the Sun, and the Pink Moon is full on April 20. Saturn is lost in the Sun’s glare, with its conjunction on April 7. Mercury is also lost in the glare, reaching superior conjunction on April 28.

For phases in any month, the moon phase guide has the full calendar.

1. Log a kōlea’s last day. Pick a lawn bird and note the date it is gone, then report it to the Kōlea Count.
2. Join the City Nature Challenge. The global photo contest runs April 30 through May 3, 2027, with identification from May 4 to 16, according to the organizers. Check their list of participating cities, and use iNaturalist to record anything wild even where no city is signed up.
3. Mark Earth Day on Thursday, April 22. Hawaii’s own Arbor Day is not in April: DLNR says it falls on the first Friday in November, when the rainy season begins, so April is a good month to scout where a tree might go.
4. Stroll the Keālia boardwalk on Maui, scanning the mudflats for stilts, and ask at the visitor center, which the refuge says opens on the first Saturday of each month (check the date first).
5. Listen to a dawn chorus on a forest trail, and brush your boots clean first.
6. Watch the Pink Moon come up at dusk on April 20, then look for Jupiter high in the east.

A Naturalist’s Field Journal holds the tallies and sketches, and the nature guides for the other states follow the same calendar. Last month’s page is Hawaii in March.

• Hunting and blaze orange. DLNR’s 2027 Lānaʻi axis deer announcement puts the general rifle hunt on eleven weekends in a row, Friday to Sunday, from March 19 until May 30, in Hunting Units 1 and 2. That covers every April weekend: April 2 to 4, 9 to 11, 16 to 18, 23 to 25, and April 30 to May 2. It is a lottery hunt, DLNR says it may be modified or cancelled at any time, and the announcement requires blaze orange for youth hunters and their accompanying adults. Separately, the state’s game bird rule requires anyone hunting or accompanying a hunter where firearms are allowed to wear a blaze-orange outer garment, visible from front and back, with no orange camouflage, and carves out spring turkey hunting and designated archery areas. Anyone on a Lānaʻi trail at a weekend this month should wear something bright.
• Spring turkey. The rule chart on DLNR’s site, dated 2013, shows a spring turkey season for Hawaiʻi Island’s hunting units A, F and G, plus private lands, ending April 15 in that year, with a permit and tag required, no dogs, and three bearded turkeys per season. DLNR had posted no 2027 announcement as of early October 2026, so confirm the dates with the Hawaiʻi Island office at 808-974-4221.
• Box jellyfish. The state’s ocean safety office says box jellyfish arrive on south and leeward shores 9 to 10 days after a full moon, and a University of Hawaiʻi study gives 8 to 10 days. With the full moon on April 20, that points to about April 28 to 30, and the next window to the end of May. Stings can cause severe injury and scarring. Check the Waikīkī Aquarium’s calendar and the warning signs, and see a lifeguard if you are stung.
• Fishing closures. The state’s fishing regulations say spiny lobster and slipper lobster are closed May through August and Kona crab May through September, so April is the last open month for all three. Female spiny lobsters cannot be taken, and all three have minimum sizes.
• Tsunami and sirens. Know your zone, and treat any siren outside the monthly test as a cue to check official information.
• Flash floods. Streams can rise in minutes from rain miles uphill. Stay out of channels when it rains.
• Winter surf. April is the last month of the winter surf season on north and west shores, so use guarded beaches.
• Volcanic gas and summit conditions. Check air quality before visiting Hawaiʻi Volcanoes National Park, and dress warmly: on Haleakalā at 7,000 feet, the normal April low is about 44 °F.