We have entered what is my favorite time of year -- early to mid October.  The days are still comfortable, but the nights are crisp and chilly.  What puts the icing on the cake is...the changing leaves.

While the cooler weather of late is helping to speed along the color change, it is not the primary mechanism.  Instead, it's the sunlight, or the lack thereof, which causes the change.  As you probably learned sometime in grade school, chlorophyll allows plants to absorb energy from light, which in this case is the sun.  As the days get shorter (we were getting more than 15 hours of daylight in June, we're now getting less than 12), plants are not getting as much light.  When this happens, chlorophyll production slows down and eventually comes to a halt.  Since chlorophyll is the primary pigment that makes the leaves green, the halt of chlorophyll production produces the change in color.

When will the peak colors occur?  The higher elevations and areas north of Interstate 80 will likely peak next week.  For much of the rest of the region, peak color will be reached around Columbus Day weekend. 

Below are two images from Accuweather.com.  The top one will continually update and shows the current color.  The bottom shows what time of year the peak colors occur.