I noticed, today, that a cool, odorless smoke or steam was coming through my AC vents and disappearing into the air almost immediately.

I was driving about 70mph down the freeway for maybe 7-8 minutes when this started happening but had been driving for approximately 25-30 minutes on city roads beforehand. The smoke/steam comes through only when the AC is pressed in. When I turned off the AC but kept the fans on, the smoke/steam stopped. I pressed the AC button back in, and the smoke/steam started again. I did not conduct further tests with keeping the AC button pressed in, the fans on, but switching back and forth between bringing in outside air or recycling the inside air. There is no performance loss nor did the temperature gauge rise while driving or while idle at a light when the AC is on and the smoke/steam is coming through.

Shortly thereafter, I arrived at home, popped the hood, and there was no smoke or excessive heat under the hood. The radiator reservoir is at an appropriate level for a warmed up engine and the temperature gauge in the dashboard was at the mid-way mark as well. The engine and hoses are clean and show no obvious signs of oil leaks. After about 10 minutes with the engine off while performing the visual inspection, I turned the engine back with the car parked for about another 5 minutes trying to recreate the smoke/steam, but it did not reoccur. I'm assuming, if I had test driven it for about 20-30 minutes, it would've happened again.

It was about 97 degrees this morning at 7:30 am when the drive took place in phoenix. It is monsoon season so there is above average moisture in the air compared to the 340 days of the year with no moisture.

All my research online indicates that my specific scenario occurs from time to time when the AC runs cool and it has been raining out. However, these were responses on other forums that did not deal with a corolla specifically.

Any ideas?

It definitely sounds like steam from condensation. It's like when you land in a plane in a hot humid place, the steam just pours threw the vents. When hot humid air meets cool dry air it makes "clouds". Got your own little cold front going in your car...LOL.

Thanks for the reassuring and timely response.

I'm sure if it happens again, the variables will be very similar. If it leads to anything else, I'll report back here for future researchers with the same issue.

Toyota Corolla 2008. I experienced the same problem today. Driving on I-4 @ 70 mph 82F. Turned on the A/C full cold and I found smoke started coming out from the A/C vents. I turned the A/C off and the smoke subsided. I tried it in the parking lot. It didnt happen. It has never happened before. I got 31,000+ miles on the car. pretty new. Please let know what could be the root-cause.
Thanks

Hi,I live on island of Malta in Mediteranean sea.Usually the humidity is very high throughout a whole year.
Last five years driving around my Corolla 2004 and every summer going overland.,via Sicily,Italy and around Europe,mostly July and August,once rainy september,driving on the highways at average speed 120 km/h and more,my AC,manuel type, was always working perfectly and beeing used for 12 hours per day,for a month or so in one go,never any problem.
This summer,however,on the second day driving overland,hot italian summer,but fantastic autostradas,with AC on, I noticed that the air flow was gradualy diminishing from dash vents,so I had to increase fan to 3,4 and than some odourless steam started coming out of vents.It was still cool air but not as it is usually.From time to time I heard the sort of rumbling sound behind the dashboard,in front of the driver side.I stopped,removed a interior filter,behind glove comprt,even this was just changed at service days earlier,restarted my trip.Everything was back to normal but for half an hour,than the same.
So I kept driving,switching AC off and on and it was always helping.
When back to Malta,only once,thou short distances,this thing with steam happened again.
Car was in Toyota service in Malta,level of freon ok,compressor,ok,valves as well.
AC now works fine,filter i did put back the very next day when this was happening because i relized that it was not the problem.
To mention as well that this problem occured in hot dry days,not humidThe official Toyota service has no explanation for this problem
Anyone have any idea how to explain this?
Thanks,regards