What happens when you ask a Siri unit on an iPhone4s, a paradox?
I think you're confusing Siri with some sort of science fiction robot.
And by the way,
1 - Although nothing can travel the speed of light, if a car were traveling the speed of light Einstein's postulate dictates it would still travel the speed of light away from the car.
2 - 0 degrees is still a finite temperature, since the Fahrenheit system is not based on absolute zero.
Just saying "What's the weather like in ...." works for me. I'm not sure why yours doesn't work. It used the built in weather app so no need for any new ones. Maybe yours just doesnt like the weather?!