Well, what you can fucking do is wait. It's going to be difficult to force flower outdoors when the sun doesn't respond to the needs of a single plant.

What you could try to do is make a tipi style tent from some very blacked out materials, like a couple tarps -- anything to keep the light out.

You'll need to only let the plant get a maximum of twelve hours sunlight, so you'll have to put the tent up for a minimum of twelve hours; then take the tent down in the morning so it gets ten - twelve hours of light again; then repeat from step one.

Tedious, arduous, and better left to nature.

Next time, try using some auto-flowering strains of the ruderalis hybrid kind.