why are all the oak trees still green?

Yes, but usually that doesnt matter.. Trees always loose their leaves in nov, regardless of the temperature... its a natural, seasonal, thing..

We've had several years in a row of warmer than normal temps this late in the season.
I think you are just using "what you think should happen" as your basis i.e., it's a timing thing not a climate thing.

Here you go from a Texas A&M researcher

https://www.kut.org/austin/2024-11-21/austin-tx-trees-fall-colors-leaves-weather-heat-drought

It's finally starting to feel like fall in Austin, but it's not starting to look like it.
Austin's trees are either still donning green leaves or have already gone bare. Why isn't Austin seeing brilliant fall foliage like in previous years?
The root cause if you will is the exceptionally hot fall Central Texas saw this year. The average daily high temperature in October was 91.6 degrees.
"A lot of trees have been stressed because of the heat and drought through September, October, November," Karl Flocke, a program leader with the Texas A&M Forest Service, said.
Trees need a combination of rain and cold to reveal vibrant colors. Chilly weather and shorter days signal that winter is coming and it's time to stop producing chlorophyll the stuff that makes plants green.
"The leaf is not actually changing colors to red or yellow, what's happening is the green is going away and you're seeing the underlying other pigmentation within that leaf," Flocke said.
But extreme heat and drought disrupt this process.
"They're losing a lot of water through these leaves so they drop them as a conversation method," Flocke said.
As for the trees that still have green leaves, Flocke says it simply hasn't gotten cold enough yet for them to change colors.
The cold snap coming through this week could turn things around. Flocke said in 2022, he doubted Austin would see any fall foliage.
"Things looked pretty crummy all the way into mid-November, when we had a really hard freeze followed by some soaking rain," he said. "At the end of November, start of December … it turned around."
If temperatures stay low and the region gets more rainfall, fall colors are still possible.
"Folks that really love fall, keep your fingers crossed," Flocke said. "We might see something happen here in the next couple weeks."

I have 5 oak trees in my yard, Blackjack, Water Oak and live oak. One of blackjacks has lost almost all the leave... the others are still all green.

Lots of oaks don't shed their leaves until spring.

My elms turned gold this week. All my oaks are live oaks so I don't expect them to right now.

My post oaks are slowly browning and dropping some leaves. The red oak and water oak still haven't figured out that Santa will be here in less than 3 weeks.

There are only two seasons for the Great Plains... Summer and Winter. It confuses the hell out of the trees here. You get used to it.

I have a plum tree that has started flowering...in December. Seems odd to me.

Azaleas blooming in Huntsville last week. Pear trees blooming in College Station. I saw a hummingbird just a couple weeks ago.

Wait until August when the temps change and all the leaves turn colors...as in brown and fall off due to the 100 plus degrees. That's our new fall season!

The leaves will be brown tomorrow after the near freezing temps tonight....then will fall off tuesday night/wednesday morning

studioone said:

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why are all the oak trees still green?

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Because its not July and its not yet Fall. This area gets brown at least twice a year during two of the 12 seasons we enjoy.

I honestly love B/CS and its always been home....but our weather used to be significantly more consistent year to year.
I feel for anyone going to Santa's Wonderland and having to wear shorts. That's just depressing.