It was dusk.

>For sure it's a wide-angle shot, that helps give the cloud a "looming" effect. The image quality is decent in the middle (e.g. antenna tower) but drops a lot out to the edges, for example you can hardly read the Wells Fargo sign to the right on top of the office tower. Implies a low-quality lens, low pixel count sensor, small sensor size, or all three.
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>Although there is some ambient light, there are significant pools of light under each street lamp. Implies either dusk or dawn. I can't tell if it's dawn with the storm approaching from the east, or dusk with the storm approaching from the west. Could probably figure it out with Google Street View and a little time, maybe even figure out the exact location of the photographer.
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>Flash is impossible for a large scene like this so to get decent exposure the ISO may have been cranked up and/or a large aperture selected, both of which would reduce image quality. Even with all that the final image was probably darker than what we see here. I suspect the brightness/gamma of the image were adjusted afterwards.
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>Superficially it doesn't look like a long exposure was used, there are few vehicles on the streets but I don't see any motion blur, and the storm clouds show some detail that might get blurred with a long exposure. Not seeing any overall blurring due to motion during the exposure.