As temperatures begin to cool, trees across the U.S. will start to sprout bright leaves of various colors. But where and when can fall lovers spot the best fall foliage this year?

According to The Old Farmer’s Almanac, leaves can change color from mid-September through early November. Depending on local weather conditions, the second and third weeks of October are “peak” times.

The Science Behind Fall Color

The timing of fall foliage is controlled by daylight and temperature. When days are warm and sunny and nights are cool, that’s when peak fall colors are revealed, according to The Weather Channel. The further north and higher in elevation a tree is, the earlier its leaves will change color.

When fall days get shorter, photosynthesis stops and leaves no longer need excess stores of chlorophyll. As concentrations of chlorophyll diminish, less concentrated chemicals like anthocyanin and carotenoids dominate, turning leaves red, yellow, or orange.

Tree species also plays a factor in the timing of color changes. This can also impact the array of colors. For example, the Northeast, which has an abundance of maple trees, contains primarily vibrant red foliage.

An area’s “peak” fall foliage occurs when the majority of trees have full canopies of colorful leaves. Rainfall can also impact fall foliage as drought, excessive rainfall, or warm periods can mute fall colors. This may impact the yield of colors this year as the Climate Prediction Center predicts a warmer-than-average fall for almost half of the U.S.

When Does Peak Arrive?

According to USA Today, most of the U.S., including the Northeast, Midwest, and Western states, will experience fall foliage peak in October. A few less populated areas will peak in September, and the southernmost states won’t peak until mid-November.

Areas like New Hampshire, Northern Vermont, and northwestern Maine will experience a peak in early October, while areas like Pennsylvania, New York, and Massachusetts will peak later in the month. While Golden Aspens in the west will peak in late September and early October, northwestern areas with lower elevations will peak in late October and early November.

“We expect vibrant colors across much of New England and the Midwest this autumn,” said Accuweather’s Paul Pastelok. He also predicted that heavy rainfalls from the spring and summer will lead to dull colors in areas like the Appalachian and Smoky Mountains.

Fall foliage watchers can use this interactive map by Smoky Mountains to track predicted peaks. Here’s a breakdown of foliage times and vibrancy, courtesy of Accuweather: