The front of the car was completely crushed by the trunk - meaning she would have been killed if the vehicle was just a few yards further along the road.
She suffered only shock during the incident at 10.30am on Sunday and the grandmother-of-six says she is ''very lucky to be alive''.
Mrs Challinor, of Cheltenham, Glos., said: ''I feel incredibly fortunate. If the tree had come down half a second later I would have been killed.
''The whole thing is a blur because it happened so quickly. I just remember coming to an immediate stop with the huge trunk smashing into the bonnet.
''I was frozen in shock until the police and fire service came to release me.
''I was sorry not to make it to church but I think someone may have been looking down on me after all.''
Mrs Challinor was hit by the falling tree - which was felled by 60mph winds - as she drove past Cheltenham College Junior School on her way to church on Sunday.
The trunk destroyed a 6ft wall before smashing onto the bonnet of the mint green car.
She was eventually freed by firefighters and paramedics but did not require hospital treatment.
Inspector Ian Phillips, of Gloucestershire Police, said: ''The lady in the car was fully conscious and talking, but was in shock.
''We were called out to respond to several incidents throughout the day, with cables and trees falling down in various parts of the county due to high winds.'

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http://www.telegraph.co.uk/topics/weath ... ntion.html