Get ready, leaf-peepers, it’s fall foliage season.

As pumpkin flavors permeate coffee shops and the morning air crispens, trees’ leaves have begun transitioning from green to shades of red, orange and yellow.

When drought occurs, like this year in much of Maryland, stress causes leaves to drop earlier and have less vibrant colors. The timing of the leaves changing depends on many factors, including temperature, light and water supply. During the summer, the green chlorophyll in leaves makes food for trees. But in fall, trees begin to go dormant and reveal their leaves’ underlying colors that existed below the chlorophyll.

Entering this week, most of the state had little to no fall color, but low color is making its way — a bit early — into the western jurisdictions where colors typically change first. Around half of the state is expected to have low color over the next week with moderate fall color creeping into Garrett County, according to a forecast from Explore Fall, a website that models fall foliage using temperature, precipitation and daylight data.

Outlook for the season

Maryland’s statewide forecasted peak is around October 21 to 25, according to SmokyMountains.com‘s fall foliage forecast for the U.S. The annual forecast model incorporates factors including historical temperature and precipitation, forecasted temperature and precipitation, the prominent type of tree in a region and historical trends.

Forecasted fall foliage

If it seemed as though trees were beginning to change early, that’s because they have been in western parts of the state.

Some parts of Garrett County were two weeks ahead of schedule, Melissa Nash, a forester for the Maryland Department of Natural Resources, wrote in the department’s annual fall foliage preview. This is a result of extreme drought in the region. When trees are stressed because of drought, they might shut down the food-making process early.

The best fall color occurs when there are cool nights and warm, sunny days with intermittent rain, Nash told The Baltimore Sun.

“We’ve been getting those warm, sunny days and cool nights here in Garrett County, but we haven’t been getting the rain,” Nash said earlier in September. “I think it’s still going to be a nice color season. It’s just going to be a little more muted out here than what we would typically expect, and we may see the peak a little bit sooner.”

Statewide, people can expect to see Maryland’s trees have more yellow and gold tones instead of red and purple, according to the preview.

This is also a result of not having enough water. Carotene, which produces the yellows and oranges in leaves, is already present under chlorophyll. Anthocyanin, responsible for reds, is produced by trees when the green chlorophyll breaks down.

The ideal weather Nash described promotes production of the red anthocyanin in leaves, but hotter days and warm nights because of the drought lead to fewer red and more yellow and orange leaves.

At least a third of Maryland has had little or no break from abnormally dry conditions since May, with conditions as bad as an exceptional drought in some areas since July. In July, almost the entire state experienced at least abnormally dry conditions.

Extreme drought conditions have impacted the western part of the state the most, where Nash is based, with drought data as of mid-September showing extreme drought in Western Maryland.