SIOUX CITY, Iowa (KCAU) — It’s that time of the year again. Temperatures begin to fall. The warm summer days are gradually traded for the cool, crisp air of an autumn day. And inevitably, the sunrise comes later, sunset comes earlier and our days quickly grow shorter and shorter as we inch closer and closer to the frigid return of winter.

But just how much daylight do we lose? And why exactly do we lose it?

Our days get shorter due simply to the fact that Earth’s axis is beginning to tilt away from the sun. As the Earth slowly tilts away from the sun the days get shorter because the greater the northern hemisphere is tilted away, the shorter the daylength. Likewise the more the northern hemisphere is tilted towards the sun, the longer the daylength is.

From summer solstice to winter solstice, the Earth’s axis is slowly tilting away from the sun and daylengths in the northern hemisphere get shorter, meanwhile, the opposite occurs in the southern hemisphere.. However, at the autumnal (and spring) equinox, the earth’s axis is not tilted towards or away from the sun, which means nearly equal amounts of daytime and nighttime in both hemispheres.

From summer solstice (June 21st this year) through the fall equinox (Saturday, September 23rd), the axis begins its tilt away from the sun and days start to get shorter as the earth’s, resulting in consistently decreasing amounts of daylight and increasing night length.

Daylength continues to decrease through the winter solstice, which this year will take place on Thursday, December 21st.

After that, daylengths begin to gradually increase again as the Earth’s axis begins to tilt back towards the sun.

Through the month of September (September 1st-September 30th), we lose approximately 1 hour and 23 minutes. Of that, we’ve already lost about 39 minutes so far (through September 15th). By the first day of fall on Saturday, September 23rd, we will have lost over an hour of daylight (~1 hour 2 minutes). That’s around 2 to 3 minutes per day.

From now (September 15th) through September 30th, we will lose 44 more minutes of daylight.

As we continue through the end of the year, we continue losing daylight. From October 1st through October 31st, around an hour and 22 minutes of daylight is lost, or between 2 to 3 minutes per day.

Heading into November, we continue to lose daylight, but as we continue through the month, we begin to lose it a bit more slowly, around 2 minutes per day and by the end of the month only between 1 to 2 minutes of daylight is lost per day.

Daylight loss continues through the first half of December ahead of the winter solstice (first day of winter). After that, we begin to very slowly gain daylight once again, only losing a total of around 11 minutes of daylight through the month of December.

In total, from summer solstice to winter solstice this year (June 21st-December 21st), we lose a total of 6 hours 15 minutes and 39 seconds of daylight.

From the fall equinox (September 23rd) to winter solstice (December 21st), we lose approximately 3 hours and 4 minutes of daylight.

On the first day of fall, we’ll have around 12 hours and 7 minutes of daylight, compared to only 9 hours and 3 minutes of daylight on the first day of winter. In comparison, we saw around 15 hours and 18 minutes of daylight on the first day of summer and about 12 hours and 8 minutes of daylight on the first day of spring this year (March 20th).