(WJET/WFXP/YourErie.com) — The leaves are starting to change in parts of Pennsylvania and the Pennsylvania Department of Conservation and Natural Resources (DCNR) has released its first fall foliage map of the season.

This year, the first day of fall fell on Saturday, Sept. 23.

The PA Fall Foliage map shows the northern border of the state as approaching its best color. Here in Northwestern Pennsylvania we are just starting to change.

As stated in the Fall Foliage report for the week of Sept. 28-Oct. 4, 2023, “the district manager in Cornplanter State Forest (representing Warren, Crawford, and Erie counties) said last week’s warm, sunny days and cooler nights initiated noticeable color changes in northwestern Pennsylvania. In a preview of what is to come, hillsides and forests are dotted and blushed with color. Some sumacs are beginning to display their brilliant red color, while scattered maples are showing a mix of red, orange, and yellow. Virginia creeper vine is also sporting its fall color, especially against dark backgrounds.”

There aren’t any Pennsylvania counties at peak color just yet, according to the Pa Fall Foliage report. The majority of the state is starting to change color, while the southeastern part of the state is seeing no change so far.

The Smoky Mountain Fall Foliage Prediction Map for 2023 is interactive, allowing users to view a prediction of when their area will see its fall foliage peak.

The interactive map shows Erie County at peak color the week of Oct. 2. Surrounding counites in NWPA are expected to reach their peak the week of Oct. 9.

By Halloween (Oct. 31), the entire state of Pennsylvania, and northern border of the U.S. should be past its peak.

By Nov. 21, the entire U.S. is expected to be past its peak, aside from the southernmost part of the U.S. along the Gulf of Mexico. That is when parts of Texas, Louisiana, and Florida will be at or near peak.

So why do leaves change color?

The Smithsonian reports as the season changes, temperatures drop and days get shorter so trees get less direct sunlight, and the chlorophyll in the leaves breaks down.

The lack of chlorophyll reveals the yellow and orange pigments that were already in the leaves but masked during the warmer months. Darker red leaves are the result of a chemical change: Sugars that can get trapped in the leaves produce new pigments (called anthocyanins) that weren’t part of the leaf in the growing season. 

The Pennsylvania DCNR reports Pennsylvania has a longer and more varied fall foliage season than any other state in the nation — or anywhere in the world. Only three regions of the world support deciduous forests that display fall autumn color:

  • Eastern North America
  • The British Isles and parts of northwestern Europe
  • Northeastern China and northern Japan

Forests in other regions are either tropical or dominated by conifers.

The best fall colors are produced when the weather is dry, sunny and cool. Places that are cloudy, damp or warm won’t see the same degree of changing color.