Did the traffic jam save Houston from Hurricane Rita?

My friend Johan suggested this elsewhere and so I wanted to take the risk of posing it to Kossacks.

Assume 1 million cars exiting Houston (and not getting very far) while also burning let's say 20 gallons of gas per car over Wednesday and Thursday last week.  With a gallon of burnt gas producing 125,000 BTU, and 1,000,000 cars burning 20 such gallons, the combined traffic jam would locally produce 2,500,000,000,000 (2.5 trillion) BTU.  A BTU is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit -- 2.5 trillion BTU is a LOT of heat.

Could that much heat released into the atmosphere local to Houston have strengthened the area of high pressure over the region enough that Rita turned eastwards, avoiding Houston? If so, the process of evacuation itself may have had a positive impact!

Update [2005-9-27 19:31:28 by martini]: Just wanted to point out that The Urban Heat Island effect is pretty well documented.