纳什维尔, 费城, and Baltimore are all enjoying the fall temperatures this weekend, but it will be a brief reprieve before warmer temperatures return early this week.
The Climate Prediction Center’s (CPC) extended one month outlook for October is showing a similar story for most of the country — above average temperatures.
The CPC shows a stretch of above average temperatures from Maine back through southern California
. 事实上, Alaska is the only state on its map that shows below average forecast temperatures during October
Fall foliage impacted by drought
When you think of fall, the first thing that usually comes to mind is leaves changing to beautiful reds, oranges and yellows. This year’s colors may look a little different thanks to the drought.
Perfect foliage conditions rely on a good combination of temperature and moisture. The processes in photosynthesis use different chemical compounds that create different colors. Most of the chemicals need sunshine to create vibrant colorful displays during autumn. But sunshine alone is not enough; trees also need rain.
The problem this year is that some areas have experienced extreme conditions, particularly in the West.
A lack of rain in the West will cause many trees, especially shallow-rooted ones like maples or birches, to go into survival mode, “shutting down” early and preparing for winter.
This stressful condition causes leaves to turn brown and fall off before they reach their peak color. The leaves that do change color will do so very briefly and can have more muted colors than normal.
Not all drought is bad
. Mild drought can actually trigger more vibrant colors
, though a lot of this depends on how much rain fell the year before
. The weather during previous growing seasons can have a delayed effect
The duration of the leaf color can be affected by causing leaves to fall off prematurely
. Prolonged and extreme drought can cause physical damage
, making it harder for trees to protect themselves against pests and disease
, and slowing their overall growth
Some locations will probably see fall colors earlier than usual this year, and they won’t last as long as previous years.