So... you're leaving for Maui in 3 days and the online web-based weather forecast shows rain every day and now you're starting to panic.

Well, stop it!

The most reliable weather sites for Maui are www.hawaiiweathertoday.com and www.noaa.gov/index.html. Either one will give you a far more accurate weather forecast than that found on your run-of-the-mill generalized weather sites.

If you want to know more about why the usual sites used for weather info won't work in the islands, read on:

First off - with a very few exceptions, online weather forecasts for Maui are nearly worthless. The most commonly used site, weather.com, is notoriously unreliable when it comes to Maui weather - and they're not alone. The fact is most online weather sites get Maui weather all wrong on a routine basis. How can this be, you say - weather.com is used by nearly everyone and is widely trusted. To fully understand why this is, you've got to have at least a basic understanding of the geography of the island. Why? Because the geography dictates nearly every aspect of the weather on the island. Maui's winds, like those in many tropical locations, are remarkably consistant. These winds, known as the tradewinds, follow much the same pattern each and every day,  starting out calm and picking up as the day heats up. They also almost always blow from the same direction - the north east. What this means, on an island like Maui which has very high mountains, is that nearly the same weather pattern repeats itself day after day. These patterns are disrupted when a major weather system approaches, this would be a tropical storm or a small front comes in from the north west, but otherwise are very reliable.

Almost every single day, this is what happens: The day starts with no wind - the air warm, humid and calm. As the day heats up the winds pick up - the hotter the day gets, the stronger the winds blow - providing a sort of natural air-conditioning that keeps it pleasant nearly all the time. Now remember, these winds almost always blow from same direction, the north east - and since it's warm and tropical and the winds are blowing over the open ocean, the air is thick with moisture. As the winds approach the island, they are forced up and over the interior mountains - and as they do so, the air cools, clouds form and rain falls. This is what gives the northern and eastern shores of Maui it's lush, tropical appearance. The windward sides of the island are greener and more tropical-looking because they gets a lot of rain. The beaches there also tend to be rockier and the water rougher and more dangerous because that same wind drives the waves up against the shore, eroding it and creating rocky cliffs instead of soft sandy beaches. These beaches therefore are often very dangerous and generally unswimable.

Now on the leeward, or downwind, part of the island, the opposite effects hold true. As the air rolls down the back side of the mountain, it's no longer so laden with moisture, since most of what it held has already been dropped as rain on the way up the mountains' north and eastern slopes. Some rain may still be falling as the air begins its trip down this other side of the mountain, but it usually peters out by the time the elevation drops to 2,000 feet or so. Thus the south and west sides of the mountains tend to be dryer - and as the air drops lower and lower down the mountainsides it warms up due to atmospheric compression - so the north and east sides of the mountains are rainy, lush and green and the south and west sides are warmer and warmer and dryer and dryer the lower you go.  Also, since the interior mountains block much of the wind, the waters on the south and especially west sides tend to be somewhat calmer and therefore with sandier beaches.

So, it is no coincidence that the resort areas of Maui on are the south and westward-facing beaches. Protected from both rain, and the worst of the wind, by the mountains, these areas have great beaches (with the calmest waters) and typically sunny, warm weather. Since there are two distinct lobes of Maui, each with their own set of interior peaks (West Maui has Kahalawai, aka West Maui Mountains, and South Maui has the huge bulk of Haleakala), there are two seperate resort areas - both with westward-facing beaches, both with fairly sunny weather. These areas are Lahaina/Ka'anapali/Kapalua in the West Maui lobe (where it is very sunny), and Makena/Wailea/Kihei in the South Maui lobe (where it is extremely sunny - almost desert-like actually).

Okay, you ask, all this is well and good, but why does that make Maui weather forecasts so unreliable? The answer is really very simple. General weather sites like weather.com don't really differentiate between all these different areas. Because of the extreme changes in elevation and subsequently climate, Maui has over twenty microclimates. If you are in Kihei for example, a mere mile away, on the slopes of Haleakala above you, it can be pouring rain all day long, but down at the beach where you are, it can be sunny and dry as a bone. Therefore a weather forecast for one area of Maui is completely irrelevant for another.

This is where the general weather sites such as weather.com fall short. The main weather reporting station on Maui is, as usual, located at the main airport. This places it in Kahului, which is on the north shore of the dry central valley. The lusher, greener and rainy side of the island is east of the airport. The mileage between the airport and resorts are not great, and in most places the airport weather there would extend out to those resort areas, but not on Maui. Those places have an entirely different climate, with an entirely different forecast. - one that is not shown on those generalized national weather sites. These sites usually take the Kahului forecast and apply it to the entire island - which makes the forecast virtually worthless for most visitors.

So, you ask, how do I tell what the weather is really likely to be?

Well, first off, you need to stop looking at those general weather sites and take a peek a site specifically geared towards Hawaii as given at the beginning of the article.. 

Secondly, remember that the tourist areas (i.e.; the beaches) lie in very sunny areas of the island, so all things being equal, the chances are pretty good that you're still likely to get quite a bit of sun no matter what the forecasts say. Yes, you do sometimes get extended periods of rain there in Napili and Kapalua and at night, but by and large both West Maui (especially the nearer you are to Lahaina) and South Maui have very, very nice weather year round.

Thirdly, it's important to note that most of the time, rain on Maui often falls in the form of heavy but brief showers that move in, dump their rain and move on. Because this rain usually originates in a specific cloud rather than a ceiling of clouds that extends from horizon to horizon, once the individual cloud passes over, the rain stops. This often happens in 20 minutes or less. Also, again, since these types of showers come from an an individual cloud, even though it is raining where you are, it can be dry maybe only a mile or so away (remember all those microclimates I mentioned) - so you often have the option of getting in your car and driving to another part of the island where the weather is better. This is particularly true if you happen to be in the Kapalua area, which gets less of the "rain shadow" effect from the West Maui Mountains. Kapalua is greener than nearby Ka'anapali because it does tend to get more rain. So... if you are in Kapalua and are getting some rain, try heading south a couple of miles to dryer, sunnier Lahaina/Ka'anapali. You  might even consider making the drive down to South Maui, where it happens to be dryer yet. In any event, though it does happen, it's pretty rare of all of both South and West Maui to be in the rain, so if you hit a stretch of wet weather, be prepared to be a bit flexable and take advantage of those Hawaiian microclimates.

Finally - at least to see what the weather is right now - is to take a look at one of the many Maui webcam sites. It's always interesting to see a web-based forecast calling for a 60+ % chance of rain, while a live webcam shows nothing but clear blue skies. Live Maui cams

Ah, Maui. Gotta love it.