You savor a breath of surprisingly cool air in the early morning.
You notice a slight change in the angle of sunlight gilding a mountain ridge.
You glimpse a first hint of yellow in the leaves of trees.
Autumn is in the air. Even here in the hot desert, with a dozen days of summer to go.
The signs of the coming season are subtle - but clear to the senses.
Meteorologists watch these things, and they have some explanations.
"The days are getting shorter. It's a longer night now, with a longer period of cooling, and that can leave the mornings feeling a little cooler," said Ken Drozd, warning coordination meteorologist with the National Weather Service.
Drozd, like many other Tucsonans, appreciates the beauty of long rays of sunlight kissing the mountains at sunset. The effect is dramatic even if the cause is fairly obvious.
"You get that more-angled light because the sun isn't so directly overhead at this time of year," Drozd said.
Erin Jordan, a meteorologist with KOLD Channel 13, said a decrease in the hours of daylight with each passing day also plays a role in producing colorful leaves. Those winsome leaves show up not only in our nearby mountains but also along watercourses and parks in Tucson.
"The trees and shrubs that shed their leaves for the winter start producing less chlorophyll as the nights get longer," Jordan said. "The plants need that extra sunshine to keep the chlorophyll production going strong, which keeps the leaves a nice, bright green. With shorter days and longer nights, that chlorophyll production slows and eventually shuts down. The leaves then turn beautiful shades of yellow, orange and red."
Jordan has more than just a ballpark estimate on the rate at which we lose daylight at this time of year.
"Between Monday (today) and the first day of fall on Sept. 22, we are losing 23 minutes and 24 seconds of daylight from sunrise to sunset," she said.
Another sign that summer is on the wane and fall is on deck: Monsoon rains begin to fizzle.
"Even though the monsoon officially goes to Sept. 30, typically after Labor Day we see some signs of the monsoon shifting southward" - bringing drier conditions, Drozd said.
He said recent rainy weather is expected to give way to a drying trend near the end of this week.
find a hint of fall
First signs of autumn color are showing up now along some watercourses and park paths in the Tucson area. It's too early to see trees in full fall flush, but here are some places to spot a few early yellow leaves:
• Agua Caliente Wash on Tucson's east side. Trees near the Houghton Road bridge over the wash show a bit of color.
• Fort Lowell Park at North Craycroft and East Fort Lowell roads. Trees are still mostly green, but here and there, yellow leaves have fluttered to the ground.
• Sabino Canyon northeast of Tucson. Areas along Sabino Creek in the canyon had just faint hints of color last week, but more trees there will take on autumn hues in the coming weeks.
Contact reporter Doug Kreutz at dkreutz@azstarnet.com or at 573-4192. On Twitter: @DouglasKreutz
Please Wait…