Why Does Alaska Have Really Long Days during Some Times of the Year and Really Short Days during Other Times?

Alaska typically has really long days during some times of the year and really short days during others as a result of its location in the far north, near the North Pole. This puts it very near the earth’s northernmost axis, which brings it closer to the sun when the earth tilts one way, but much farther from it when it tilts the other way. Alaskan summer days tend to be very long as a result, and in some regions the sun never sets; in the winter, though, it may never rise, or come up for only a few hours at a time. Most of the regions on the opposite side of the earth, down at the South Pole, experience very similar seasonal shifts on an inverse schedule. When Alaska is having long summer days, Antarctica and the islands surrounding it typically experience the darkness of winter, and vice versa.

The axis or tilt of the earth is what primarily accounts for the extraordinary periods of daylight and darkness at the poles because it is during these times that the land in the northern part of Alaska is tilted either directly into or far away from the sun. People often find it easiest to understand this by making or imagining a model. In the center is a sphere, like a tennis ball, with a long needle passing through its center from top to bottom. The needle extends out both “poles” creating an axis. A black line should run the circumference of the ball to indicate its “equator.” If that ball is placed on a roughly circular track and the axis is inclined 23.5 degrees towards the track, it will mimic the earth to a pretty close degree. A light source in the center will represent the sun.

As the ball moves around the track, its axis remains fixed, though by virtue of it moving around the track its inclination, relative to the center light, changes. At one point the northern pole gets greater exposure to the light. At the opposite end, though, the same northern region is pointed away from the light source with the southern pole exposed inward.

Some people mistakenly attribute seasons to the slightly elliptical orbit of the earth, believing that the closer the earth is to the sun, the warmer the days will be. In reality, earth’s orbit is nearly circular, and the small deviation in distance is not enough to cause seasonal change. The length of a day at any time of year is predominantly a factor of how close a certain location is to either of the earth’s two axes. The equator, where the seasons don’t really change and things tend to stay pretty warm, is usually the farthest point from either pole. As a result, inclination and tilt don’t make much of an impact here. Things tend to get more extreme the further north or south one goes.

This inclination of the earth is what creates the seasons, and is also responsible for Alaska's long summer days. When the North Pole is inclined inward towards the sun, the region receives extended exposure. From the viewpoint of someone standing at true north on the summer solstice, the sun raises high into the sky, and then circles the horizon without ever setting. Elongated exposure to sunlight during the summer allows the region to retain more heat. Shadows are shorter because the sun is higher overhead.

At the South Pole in Antarctica, the opposite is occurring. Here, the region is inclined away from the sun, so that on the winter solstice the sun skirts the horizons but never quite rises. In outlying regions further from “true south” where the sun does raise low in the sky for short periods of time, the sun’s angle is very oblique. This creates longer shadows, additional atmospheric filtering, and weaker radiation or warmth. Thus, when Alaska is experiencing endless summer days filled with direct light, heat and warmth, desolate Antarctica is steeped in days of near total darkness and weak sunlight. Conversely, when Antarctica sees summer, Alaska is having winter.

In spring and autumn the earth’s axis is aligned along its orbital path rather than towards or away from the sun. Hence, the sun shines most directly on the equatorial regions, or center of the earth. On the solstices that mark these seasons — March 21st and September 21st, respectively — most regions have 12-hour days and 12-hour nights. For each day that passes after a spring or fall equinox, the days begin lengthening in one hemisphere and shortening in the other.

It’s important to note that the state of Alaska is very large and covers a great deal of land. While some of the northernmost parts are within the Arctic Circle and sit very near the North Pole, there are many other parts of the state that sit much further south. As a result, seasonal generalizations can’t really be made for the state as a whole. Many Alaskans in the southernmost regions never see sunlight that lasts all night or winter days of total darkness.

Alaska is the largest state in the United States, measuring 663,300 square miles. For comparison, that is more area than the next two largest states, California and Texas, combined. The region is so extensive that it makes up multiple different climate zones ranging from maritime to continental to arctic. Due to its size, the number of hours of darkness in Alaska varies widely depending on location. Only the northernmost area of the state undergoes the extremes of daylight and dark that many mistakenly associate with the state as a whole.

The longest period of darkness in the state occurs during the winter solstice which falls near December 21 each year. The most southern areas of the state never experience the total darkness that Alaska is known for. Conversely, towns in the far north of the state experience long periods of complete darkness. Here is a sampling of the wide variety of daylight hours in Alaska during winter solstice:

Statistically, Alaskans experience less major depression than the residents of many other states. However, about 10 percent of Alaskans are impacted by seasonal affective disorder, a type of depression linked directly to insufficient exposure to sunlight. That is double the average percentage of residents experiencing SAD in other states.

Seasonal affective disorder may also be a contributing factor to the rampant levels of alcohol and drug abuse in the state. Studies estimate that an astounding 50% of Alaska residents engage in some level of binge drinking and the state ranks among the top 10 states for severe drug use. In the under-served and isolated Native populations, these statistics are even starker.

During the winter months, many Alaska residents use bright light therapy to combat the persistent darkness. They may also increase supplementation of vitamin D as well as the use of prescription anti-depressants.

Just as the amount of darkness in winter varies, so do the hours of daylight in the summer. The north gets the most extreme daylight exposure while the south experiences some hours of twilight-like darkness. Using the same sampling of locations, this is a snapshot of the state on the June 21 summer solstice:

Overwhelmingly, Alaskans love the state's long days during the summer months. Many residents embrace the ability to engage in activities whenever their schedule allows and engage in outdoor activities at all hours.

The biggest issue with the constant daylight is making the adjustment to sleeping when it isn't dark. The prolonged daylight hours can throw off the body's circadian rhythms making sleep difficult to attain. Some residents make use of blackout curtains, others may utilize sleep masks to trick the body into thinking it is dark. The majority of locals and visitors report adjusting to the long days quickly and easily.

Although locals often joke about Alaska only having two seasons, the state does have both spring and autumn. Both seasons tend to be very brief, sometimes lasting only a couple of weeks. Additionally, the rapidly changing daylight hours can make these seasons challenging to navigate.

On the spring and fall equinox, Alaska comes closest to the average day length of other states with the day split evenly between daylight and dark. Leading into both seasons, however, the daylight hours change drastically on a daily basis. The changes are so rapid that the hours of sunrise and sunset can be a full hour earlier or later each successive week.

Alaska's long summer days are due to its high latitude, which positions it within the Earth's polar circles. During summer solstice, areas above the Arctic Circle, including parts of Alaska, receive 24 hours of daylight as the Earth's axial tilt directs the North Pole towards the sun, resulting in the phenomenon known as the Midnight Sun.

In winter, Alaska's tilt away from the sun leads to extremely short days. The same axial tilt that brings summer's Midnight Sun causes the sun to barely rise above the horizon or not at all during the winter solstice period. This results in long nights and very short days, with some regions plunged into polar night, a time of continuous darkness.

The Earth's axial tilt of approximately 23.5 degrees is responsible for the seasonal variations in daylight. As the Earth orbits the sun, this tilt causes different regions to receive varying amounts of sunlight throughout the year. Alaska's high latitude amplifies these effects, leading to significant changes in day length between seasons.

Viewing the Northern Lights, or Aurora Borealis, during Alaska's long summer days is highly unlikely. The Midnight Sun creates nearly 24 hours of daylight, which outshines the auroras. The best time to witness this natural light display is during the darker months, from late September to early April, when nights are longer.

Alaska's wildlife has adapted to the extreme day length variations. Animals like the caribou and brown bears follow seasonal patterns, with caribou migrating and bears entering hibernation in sync with daylight changes. Many species also adjust their breeding and foraging behaviors to capitalize on the summer's abundance of food and light.

Alaska's day length extremes significantly influence human activities. In summer, extended daylight hours support outdoor activities, tourism, and industries like fishing and construction. Conversely, the short winter days can affect mood and productivity, leading to increased use of artificial lighting and a focus on indoor work and recreation to cope with the prolonged darkness.