Shades of Fall : Despite Summery Swelter, Trees Know When It’s Time to Turn
As the mercury climbed above the 90-degree mark again Monday, these trees provided one of the few clues that it’s actually autumn in the San Fernando Valley.
The heat does not delay the annual color change and falling of the leaves, because that is triggered not by cold but by the reduced hours of sunlight, as the autumn days grow shorter and the nights longer, said John Sherwin, meteorologist for WeatherData, which provides forecasts for The Times.
Trees rely on sunlight to manufacture chlorophyll, the substance that gives leaves their green color.
Weather conditions such as an extended dry period or an early autumn freeze can cause the leaves to turn earlier in the season and dull their colors, Sherwin said.
Though there’s little chance of a freeze, Valley residents can expect cooler temperatures later this week. High pressure lingering over the area will move east and weak Santa Ana winds will be replaced by onshore winds, Sherwin said.
High temperatures are expected to remain in the 90s today, but starting Wednesday, high temperatures will drop several degrees, Sherwin said.
High temperatures Thursday are expected to drop into the 70s in some areas of the Valley.
On Monday, Chatsworth hit a high of 97 degrees, breaking a record of 95 set in 1976. Van Nuys topped out at 95, Woodland Hills and Northridge at 94, and Burbank had a high of 93.
Newhall’s high was 87. Temperatures in Palmdale and Lancaster reached 82 and 81 respectively.
* RELATED STORY: B8
Start your day right
Sign up for Essential California for news, features and recommendations from the L.A. Times and beyond in your inbox six days a week.
You may occasionally receive promotional content from the Los Angeles Times.
