A hazy greyish, blueish, nondescript sky with the sun trying its hardest to break through and then, suddenly, the transformation to the 'eye in the sky' or halo happens. The diameter of the halo must depend on the altitude that the haze has formed at but this one was huge.
Weather and meteorological phenomena, you just can't beat them, there's even just the hint of a rainbow in the bottom quadrant too. Now for the technical bit, the halo effect is created by cirrustratus is high up in the atmosphere and the sunlight is refracted through ice crystals to give the halo.
Now you know.