Everyone has different tolerances for cold - and heat.
Even as a child in Quito, a light jacket was always enough for me. Although it could get cool at night and we had a fireplace, we did not use it that often. Even camping out on the slopes of Pichincha where we'd get a light frost in the morning, a light jacket was all that was necessary.
And no need to bring a parka with you - you can always buy stylish and unique artisan-made jackets and chompas of llama wool and ponchos in and around Quito at good prices.