Portland’s skyline ignited in orange and red hues this week, as the metro area hit its peak fall foliage season. The city is alive with the color, smells and crisp air of autumn, but 2019′s peak fall foliage only lasts for a fleeting few weeks.

People around the city have taken to posting Portland’s quintessential fall views on social media.

Portlanders -- of all shapes and sizes -- are clearly enjoying the season.

But what causes the abundance of brilliant color splashed across the city skyline? It’s not exactly the colder weather -- it’s chemicals in the leaves responding to the seasonal changes that create the chromatic displays.

Of course, it comes down to science. Leaves are the powerhouses of trees, converting sunlight into energy with a chemical called chlorophyll. Chlorophyll is the substance that gives leaves their green hues. But leaves also contain other chemicals like carotenoids, anthocyanins and flavonols.

Autumn’s shorter days and cooler temperatures act as a signal for trees, which then stop producing chlorophyll. The leaves begin to reflect the oranges, reds and yellows of the other chemicals.

Trees drop their leaves to protect their limbs from the harsh, freezing temperatures of wintertime. The connecting veins between a tree and its leaves close in the fall, cutting the leaves off from nutrients, and the leaves eventually fall to the ground.

Portland is rife with places to enjoy the short-lived fall colors -- the Portland Japanese Garden, Laurelhurst Park, and the views from Mt. Tabor -- just to name a few.

As one Reddit user put it, “Sometimes it’s nice we live in a storybook.” These fleeting fall moments are a favorite time of year for many.

Peak foliage season is only around for a few weeks. According to this Oregon fall foliage blog, it should only last for about one more. Soon, the Portland skyline will lose its brilliant hues and the city will be left with bare branches, plenty of rain and wintry, silver-grey clouds. So enjoy, Portland.

-- Emily Goodykoontz; 503-221-6652; egoodykoontz@oregonian.com