Weatherz School: Tracking changing daylight hours

Weatherz School: Tracking the changing daylight hours

Meteorologist Brandon Weatherz breaks down what determines daylight hours and sunrise times throughout the year

A sunrise can be a stunning display, but to catch one, you have to know when it’s coming. Especially here in the Northland, the time that the sun rises and sets can vary drastically depending on the time of year.

The Earth’s tilt is responsible for the seasons and the constantly changing nature of our daylight hours. The winter solstice in the Northern Hemisphere is when the sun is over its southernmost point, the Tropic of Capricorn.

Of course, every “day” is 24 hours, but if we define it as daylight hours, the winter solstice is the shortest day of the year for us. How short it is depends on latitude.

Key West, Florida still gets over ten and a half hours of daylight on the winter solstice. The further north you go, the shorter the shortest day of the year is. The Canadian border has closer to 8 hours between sunrise and sunset, which is about two and a half hours of daylight less than Key West.

The time that the sun rises and sets depends on both latitude and longitude. Even on a more local scale we see this. On December 21st, the sun rises after 8 am for International Falls and sets at 4:20 pm. Duluth sees a sunrise more than ten minutes sooner, and a sunset two minutes later.

Minneapolis’s sunrise isn’t much earlier than Duluth’s, but the sunset is twelve minutes later. Madison has a sunrise almost 40 minutes earlier than International Falls, but a sunset only five minutes later.

Let’s look at Duluth’s day length over the course of the year. On January first, we have eight and half hours of daylight and it’s 52 seconds longer than the previous day. The rate of daylight gained peaks around the equinox with each day being 3 minutes 21 seconds longer than the day before.

The rate plateaus at the solstice with June 21st being only one second longer than the previous day. The summer solstice has almost 16 hours of daylight, then days quickly get shorter through the fall.

Sunrise time is almost 8 am at the start of the year. It pulls back around 6:30 am in March, but then the start of Daylight Saving Time puts it an hour later.

By the summer solstice, the sunrise is around 5:15 am. Without DST, it would be closer to 4. Sunrise falls near 8 am into November, then the end of Daylight Saving Time sends us briefly back to a 7 am sunrise. We bottom out close to 8 am in December.

With all of that change in mind, it’s easy to imagine that if you tried to catch the sunrise at the time as a month or so ago, you’d miss it completely. And what a shame that would be.

Sunrise and sunset data was taken from