Hawaii month by month — at a glance
Hover each month for the summary. Click to pin it.
In almost any destination the first question when picking a date is what the temperature will be. In Hawaii that question has no content: the weather is practically the same all year. What changes with the season is something else, and it decides whether a beach is a place to swim or a place to stay out of.
01 Five degrees across the whole year
The Honolulu figures make it plain. The lowest average high is January and February's, 26.9 degrees; the highest, August's, 31.6. That is 4.7 degrees of travel across twelve months. Sea temperature moves even less: from 24.3 degrees in March to 26.9 in September.
Rain does have a season, though in Honolulu there is little of it: 417 millimetres a year, concentrated between October and March. It is worth adding that this figure is for a city on the leeward side, in a rain shadow; on the windward slopes of the same islands it rains vastly more.
Key moments at a glance
A 26.9-degree sea, holidays over and prices easing. The best combination of the year.
The north has eased and the south has not started. 20 millimetres of rain and very few people.
The best month for humpbacks and giant waves, and the worst for swimming in the north.
55 millimetres of rain, northern storms and the priciest fortnight of the year.
02 Winter breaks in the north
The origin of the winter swell is thousands of kilometres away: North Pacific storms, between Alaska and Japan, generate energy that travels across open ocean and reaches the islands as long, ordered waves. That is why they break on north- and west-facing coasts, and only on those.
The scale is hard to picture without numbers. Between November and February, waves on Oahu's north shore average about five metres of face, and around twenty days a season exceed eleven metres. That is why that stretch of coast is famous, and also why in those months it is not a beach.
03 Summer breaks in the south
In summer the North Pacific calms down and the other hemisphere gets to work. Storms of the southern winter, far to the south, send swell that travels thousands of kilometres and reaches the islands from the south, roughly between April and October.
The difference in magnitude is large and should not be confused. Southern swells are considerably smaller and shorter-lived than northern ones, because they have travelled further and because the southern storms are much more distant. A good south day is nothing like an average winter day in the north.
There is no beach season here. There are two, and they happen on opposite sides of the same island.
04 The same beach, two different places
From all of the above comes the most important practical consequence in this article, and it is a matter of safety. A beach that in August is a protected pool can in January be a place of strong currents and violent shorebreak, and vice versa. The photograph you saw and the reality of the day may belong to different seasons.
The rule everyone here uses is simple: in winter you swim in the south, and in summer you can swim in the north. And the practical habit worth adopting is simpler still: choose beaches with a lifeguard tower and ask before going in. High-surf advisories are published daily and change from one day to the next.
05 The other calendar: the whales
There is a second seasonal event that coincides with the northern swell and offsets many of its drawbacks. Humpback whales come to the archipelago's warm water to calve and mate between December and April, peaking between January and March.
That means winter has its own argument: whales, spectacular waves to watch from land, and windward slopes at their greenest. What it does not have is the best swimming water everywhere, and it is better to know that before arriving than to discover it there.
06 How to pick the week
If you are going for the sea and for swimming, aim at September and October: the water is at its warmest, 26.9 degrees, school holidays are over, prices drop and the south still carries some swell without it becoming a problem. April and May are the second window, with the calmest sea of the year.
If you are going for the whales or to see big waves, go between January and March and organise the trip around the south coast for swimming. Avoid the second half of December, the priciest fortnight of the year and also the peak of the storm season.
And whenever you go, check the surf forecast each morning and never assume a beach behaves as it did last time. On these islands the month tells you which side to use; the day's forecast tells you whether that side works today.
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