(NewsNation) — As we move further into the fall season, you may notice that the leaves on the trees are starting to change color.

But with warmer and drier weather conditions across much of the country, it could largely affect the vibrancy of the foliage this fall. Some said they are already seeing the fall colors, but they’re duller than last year.

Others say they are seeing trees that are just shedding their leaves before they even change color.

Areas along the Rockies and near the Canadian border are already experiencing the fall colors, with much of the rest of the northern U.S. not expected to have their peak until the end of October or later in November. Dr. Christy Rollinson, the senior forest ecologist with the Morton Arboretum, said this is a worrying trend.

“Trees need more water when it’s warmer,” Rollinson said. “With the warmer conditions we had leading into what we’re in now weren’t just warm, they were hot. And that exacerbated the lack of rain these places have gotten.”

European officials recently announced that this September was the third hottest on record globally, including above-average temperatures across much of the U.S. With the warmer-than-normal weather expected to continue for much of the central and eastern U.S. this week, fall colors could be delayed and dimmed.

Trees also need cool conditions at night for leaf colors to take effect. Meanwhile, drought conditions rapidly expanded in the past month, now encompassing 45% of the country, which can also lead to a poorer display.

However, Rollinson said the diversity of tree types means there’s bound to be at least some species that bode well this fall, and it’s not too late for some trees to display vibrant colors.

“Hope is not lost for fall color, and particularly things that are pretty drought-resilient like oak trees that are still well-primed for a great fall color show,” Rollinson said.