This is a really great start.
Now, sun rays usually appear when there's a lot of clouds, and there's just a few holes where sunlight breaks through the clouds. So compared to the dark background, the air illuminated by the sun looks brighter. And of course, there needs to be some particles in the air to catch the sunlight, so it's more likely to happen when there's a lot of moisture or dust in the air.
On such a bright and sunny day, with relatively few clouds, you don't usually see sunrays like this, I think, because everything is fairly bright anyway, and there's not enough contrast. I mean, if that cloud wasn't in front of the sun, you still wouldn't paint the sky as bright as the sunrays, probably.
Maybe I'm wrong though. Google 'sunrays', look at some pictures and see if you disagree with me.
