Extreme temperature changes are hard on batteries.  We have both extreme heat and cold here in Texas.  Our 5,000 Mile Service includes a load test on the battery to determine its state of charge.  Batteries can fail without any warning and a load test will alert us to potential starting problems down the road.  We carry Interstate batteries because we feel like they hold up better to the extreme temperature changes and to the energy demands of all the electronic features in todays Lexus.