Honolulu in May: Weather, Sea Temperature and How It Compares to April and June

HONOLULU · MAY · 21.3° N

Honolulu’s May runs warm and mostly dry at the airport gauge: an average high of 84.8°F, an average low of 71.5°F, and 0.82 inches of rain across the entire month. The ocean off the south shore averages 77.0°F. On May 15 the sun clears the horizon at 5:51 am and goes down at 7:03 pm, giving 13 hours and 12 minutes of light to a trip that is mostly about water.

What May does not give is June’s dry spell. Four weeks later the precipitation normal drops to 0.50 inches, measurable rain shows up on 0.7 days instead of 1.6, and the sea runs 1.4°F warmer. The trade goes the other way at noon, since June days average 86.9°F. April, for its part, is cooler by 1.7°F and carries more wet days, at 1.9.

On this page

• Honolulu weather in May84.8°F highs, 0.82 in of rain, 1.6 wet days
• Sea temperature for swimming77.0°F off the south shore
• Crowds, prices and the hotel taxBooking order, and the tax we did not source
• Things to do in MayWaikiki, Diamond Head, Hanauma Bay
• A two-day planBuilt around a 5:51 am sunrise and a 7:03 pm sunset
• May vs April and June84.8°F against 83.1°F and 86.9°F
• Is May a good month to visit?Yes for swimmers, with one rain caveat
• How the twelve months rankThe year-round verdict for Honolulu
• Honolulu in April0.77 in of rain, sea at 76.7°F

Where to sleep, how the twelve months stack up and what the four weeks before this one look like are handled on the year-round page and in Honolulu in April. Everything below is tied to the dates on your flight confirmation: the normals, the water, the light, and the two neighboring months you could still switch to.

Honolulu weather in May: average highs, lows and rain days

Every figure here comes from NOAA NCEI’s 1991-2020 monthly normals for station USW00022521, a real thermometer and rain gauge at Honolulu International Airport on the leeward south shore. That places the average high at 84.8°F, the average low at 71.5°F and the month’s rain at 0.82 inches. The windward side of Oahu and the mountains behind town take several times that rain, and this gauge never sees it. Read the normals above as a south-shore reading, not an island-wide one.

In an average May, 1.6 days record at least 0.10 inch of rain, which works out to measurable rain roughly one day in twenty. A day of an inch or more comes up 0.1 times per May, so about one May in ten sees one at all. In practice the month’s 0.82 inches lands on very few days, and an outdoor plan built for May is planning around a pause rather than a washout.

The gap between day and night is 13.3°F, from 84.8°F down to 71.5°F. That is one light long-sleeve layer for a pre-dawn crater climb or a breezy lanai after dinner, and nothing heavier. No jacket, no long pants for the evening, and the sunscreen matters far more than the sweater: a 21° N sun at midday does its work whether the air feels hot or not.

Light is the quiet advantage of the month. On May 15 sunrise falls at 5:51 am local and sunset at 7:03 pm, for 13 hours and 12 minutes between them. A morning that starts at six has the beach nearly to itself, and dinner at six still finishes in daylight. We did not source the civil-twilight minute, so treat the swimmable window as ending with the sun.

Can you swim in Honolulu in May? Sea temperature and what it feels like

The sea surface off Honolulu averages 77.0°F in May, from the Open-Meteo Marine API over 2015-2024. One nuance belongs with that number: it is the mean of daily maxima, so it sits a shade above a true 24-hour average. The water you meet at 6:30 am is a little cooler than 77.0°F, and the water at 3 pm a little warmer. We found no station-grade buoy series for it.

At that temperature most people walk in without the flinch step. A swim of twenty minutes needs nothing. An hour face-down on a reef is where thin swimmers start to feel it, and a rash guard solves that while doing the sunburn job at the same time. For scale, the same measure gives April 76.7°F and June 78.4°F, so the whole spring spread is under two degrees and nobody’s swim plan should hinge on it.

Wind and swell are the part we cannot chart. Our sources here carry no May wind speeds and no wave heights for Oahu, so we make no claim about which shore is working. Check the National Weather Service surf forecast on the morning you go, ask at the beach, and note that a south-shore number says nothing about the north shore forty minutes away by car.

How busy is Honolulu in May? Crowds, prices and the hotel tax

We verified no occupancy series and no monthly room-rate index, so May gets no rank against the other eleven months on price here. What the calendar says is simpler: May sits after the spring break weeks and before the mainland summer holidays, and airlines and hotels price Honolulu off that calendar rather than off the weather. Any shoulder-season line you read about the month, ours included, describes demand timing and not a quoted rate.

Book the flight first, the rental car second, the room third. That order is editorial judgment rather than a booked-rate series, and it follows from what a car does to a May day on Oahu. For Hanauma Bay Nature Preserve or the Pearl Harbor memorials, open each operator’s own booking page before you fix the itinerary: we could not source their release windows, fees or closure days, and all three change.

On taxes, plain cards on the table. Our sources carry no figure for Hawaii’s transient accommodations tax or for Honolulu County’s share of it, so we give no percentage rather than a guessed one. Assume the nightly rate on the search screen is not the line that hits your card, and ask the property for the full tax and fee breakdown before you commit to non-refundable nights.

If one line in the budget deserves the upgrade in May, make it the car rather than the ocean view. The airport’s 0.82 inches describes the leeward south shore, and the windward coast takes several times that. When a shower sets up over the Koolau side, a car moves you back around to the dry half of the island the same afternoon, while a bus itinerary spends that afternoon getting wet.

Things to do in Honolulu in May: Waikiki, Diamond Head and Hanauma Bay

May’s specific gift is the combination: water already at 77.0°F, daylight running to 7:03 pm, and days that average 84.8°F instead of June’s 86.9°F. A crater trail started at seven, with the air still near the 71.5°F overnight low, is a different exercise from the same trail in a month two degrees hotter. Long water days and a walkable morning fit into the same twenty-four hours in May.

The named targets, in order of how much the month affects them: Waikiki Beach for the 77.0°F swim and the 7:03 pm sunset, Diamond Head for the crater climb in the cool hours, Hanauma Bay Nature Preserve for the reef, Ala Moana Beach Park for flat water and shade, and the Pearl Harbor memorials for a morning that is mostly indoors and on the water. Fees, hours and reservation rules for these sites were not sourced here: check each operator.

What May actually changes at those places is the air, not the sea. Between April and June the ocean moves 1.7°F in total, from 76.7°F to 78.4°F, which no swimmer notices. The air over the same eight weeks climbs 3.8°F at midday and 3.7°F overnight, and the wet days fall from 1.9 to 0.7. The season you feel on a crater path is written in those two columns, not in the water temperature.

On free entertainment, we have nothing dated to offer and will not pretend otherwise: no May event dates and no free-admission days appear in our sources, so we name none. Check the venue calendars yourself once your dates are fixed. The reliable no-cost item is the shoreline itself in that last hour before 7:03 pm, when the light drops and the sand cools off.

Honolulu in May: a two-day itinerary

Day one, on the south shore. Up before the 5:51 am sunrise and onto the Diamond Head climb while the air is nearer 71.5°F than 84.8°F. Back down for a swim by nine, when the water has yet to reach its daily maximum of 77.0°F. Eat and stay under a roof through the 1 pm to 3 pm heat. Back in the ocean at four, then hold the beach until the 7:03 pm sunset and eat afterward, in the dark, with the day’s sun already banked.

Day two, with the car. Cross to the windward coast early, knowing that the 0.82-inch normal you read belongs to the airport and not to that side of the island. Swim, eat, and keep the afternoon loose. If the shower that falls on one May day in twenty lands on this one, drive back over to town and spend the hours indoors at the Bishop Museum or the Honolulu Museum of Art, then pick the beach back up at six.

Honolulu in May vs April and June

Read the three columns together and May lands in the middle of everything except rainfall. Its 0.82 inches is the highest total of the trio, even though its 1.6 wet days beat April’s 1.9. June takes the dry title twice over, at 0.50 inches spread across 0.7 days, and adds the warmest water at 78.4°F. Air normals for all three months come from the same NOAA station and the same 1991-2020 period, and the sea figures from the same marine series.

Shift four weeks forward and you buy a drier month and 1.4°F more warmth in the water, and you pay for it with days that run 2.1°F hotter and nights 2.3°F warmer. Shift four weeks back to April and you save 1.7°F at midday, but the rain shows up on more days and the ocean drops to 76.7°F. Nobody swims differently across that range, so the decision comes down to heat tolerance and what the flight costs.

Is May a good time to visit Honolulu?

Yes, for anyone whose trip is built around water and walking. A 77.0°F ocean, 84.8°F days, 13 hours 12 minutes of light and measurable rain on roughly one day in twenty add up to a month where almost nothing gets canceled. It is a weaker choice for a traveler who wants the driest possible week on Oahu, because May’s 0.82 inches is the wettest total of the three months compared here.

If that dryness is what you are buying, move to June: 0.50 inches, 0.7 wet days and the warmest water of the three at 78.4°F. The price of that move is heat, with days averaging 86.9°F and nights 73.8°F, and a calendar that collides with the start of the mainland summer break. April makes the opposite case on temperature and loses on rain days, at 1.9.

Against its two neighbors, May is the setting where the water is already warm enough to ignore while the midday air has not yet reached June’s numbers.

The last word

Fix the dates on heat rather than on rain: the month’s 0.82 inches will cost you a pause, not a day, while the difference between a May night at 71.5°F and a June night at 73.8°F is the one you will feel in a room with a weak air conditioner at 2 am. Book the car alongside the flight, keep the middle of the afternoon indoors, and use the hour before 7:03 pm on the sand. Then check the year-round page to see whether a different month suits you better.

Sources & data for this guide

• May air normals (high 84.8°F, low 71.5°F, 0.82 in, 1.6 days ≥ 0.10 in, 0.1 day ≥ 1.00 in) · NOAA NCEI monthly normals 1991-2020, station USW00022521, Honolulu International Airport · checked Sep 15, 2026
• April and June air normals used in the comparison table · same NOAA NCEI 1991-2020 series and station · checked Sep 15, 2026
• Sea surface 77.0°F in May, 76.7°F in April, 78.4°F in June, taken as the mean of daily maxima over 2015-2024 · Open-Meteo Marine API · checked Sep 15, 2026
• Daylight of 13 h 12 min, sunrise 5:51 am and sunset 7:03 pm local on May 15 · sunrise-sunset.org · checked Sep 15, 2026
• Scope caveat: the gauge sits on the leeward south shore, and windward Oahu takes several times its rainfall · NOAA NCEI station metadata · checked Sep 15, 2026
• Editorial admission: no occupancy series, no monthly room-rate index and no transient accommodations tax figure were sourced for this page, so none are quoted. Fees, hours and reservation rules for Diamond Head, Hanauma Bay and the Pearl Harbor memorials were not sourced either · check each operator before you book.