Well it might just be possible.
There have been only two occasions when I've seen a 'sharp edge' to the coverage of a rain cloud but I remember them both well.
The first was in Ipswich, when I was in my teens. Coming down Bishops Hill it was bright and sunny up until a clearly defined line, beyond which it was gloomy and pouring with rain. People were walking backwards and forwards between the two zones, just as if they were walking in and out of a shower. (i.e. you could stand still at one point on the pavement and be perfectly dry, in bright sunshine. Just two paces forward would take you into pouring rain. Two paces backwards would take you back into the dry again. There was no gradual transition; two people could be standing a yard apart with one person getting a sun tan and the other one getting drenched).
A few years ago I saw something similar while driving on the A14, so maybe Weatherfield was experiencing the same freak conditions? Or, of course, there could just now be an unemployed continuity assistant who used to work for Granada!
;-)