Fall equinox will soon mark shorter days, longer nights in the Pacific Northwest.

PORTLAND, Ore. (KOIN) -- It's almost time to say an official hello to fall with the Autumnal Equinox happening this Sunday.

At around 5:45 a.m., the days will start getting shorter and the nights longer in the Northern Hemisphere. According to OMSI Director of Space Science Education Jim Todd, this is the moment in time when the sun’s rays are directly over the equator and the days are nights are nearly equal in length.

However, KOIN 6 Meteorologist Kelley Bayern says that, due to several factors - such as latitude and location, as well as the bending of sunlight through our atmosphere - most locations in America don't have exactly equal daylight and nighttime hours on the date of the fall equinox.

"In Portland, we'll see 12 hours and 8 minutes of daylight on the equinox with a sunrise time at 6:58 a.m. and sunset time at 7:04 p.m. September 25 will be the day that we get closest to equal daylight and night time hours with a sunrise at 7:02 a.m. and sunset at 7:01 p.m."

Bayern added another interesting fact about the seasonal change: We are losing daylight by about three minutes every day.

"By October 30, we'll see our first sunset before 6 p.m.," she said. "A few days later, our first sunset before 5 p.m. occurs on November 3 due to Daylight Saving Time coming to an end and falling back one hour."

Overall, summery weather is likely to stick around a bit longer. In fact, Oregon could see unusually warm temperatures days after the official start of fall. Further, all of Washington and most of Oregon lands are under the “equal chances” label for a warm fall, cool fall or average fall. However, a chunk of southeastern Oregon is leaning toward a warm seasonal outlook.