You most definitely can, and won't leave behind any spots. All done traditionally. Due to the weather today, it was put to the ultimate test.
Let me explain.
House and Location
Big farm house out in the country side with a very big newly build extension. Many different angles on the house for the wind to change direction. One end of the house opens up to the driveway, and hills in the background, many trees on the hills, and along the long driveway. All other sides of the house were steep sloping farmland hills, with trees only at the very top. Picture perfect house and views. Perfect conditions for the wind to pick up debris, from the farmland, trees and road. Ultimate chance for the wind to pick up speed as well.
Weather conditions
The wind came right from the front end of the house which opens up to the driveway, through the trees and everything. Sometimes it came from a slightly different side, but always under the optimal angle, almost 90degree on the window.
Windspeeds at 30-40mph, but must have been higher, atleast the gusts of wind felt much much higher. It was one of the worst winds I've had so far here in Surrey. It was sometimes scary up the ladder, even at very low 1st floor windows. Water flying out of the bucket type of winds.
Cleaning, window types and Inspecting work
This was the first clean, windows were very dirty, and I did not clean any of the woodwork, frames or sills, or anything to begin with. No upvc frames, nice new wooden frames.
In the morning it was quite good weather, so started on the front side of the house, and worked my way along the right hand side of the house. Front was small windows, chest high, the side of the house was 5x ~7ft high french doors, with a 6ft wide half moon window above that. Very big doors. Finished those as well. Then right around a 90 degree corner slightly set back, walkway from new extension to main house. So a nice little corner there for the wind to blow, there were 3 very big shoplike windows there. Finished that, and also did some long georgian type panes that I could do with squeegee which were again right in the path of the wind. The side of the house now and then got the full blast of wind too, when it was raining especially.
The solution used was Squeegee off.
It started to rain so hard, that the windows were streaming with rain, really bad downpour and I couldn't even look inside. I had to find shelter, also because of the very high winds. I thought, oh no.....there goes the good work. The windows were soaking, literally everything. The big french doors and all the woodwork was soaking.
After the rain the sun came out, wind was still very heavy (freak weather really) Sun was quite warm, so everything started to dry again. Again, perfect conditions for the airborn debris to stick against the window.
So I went round the back of the house to clean some more windows, better finish it I thought. After that, I went back to all the windows I cleaned, and they were drying very very nicely to my suprise. Came back 15min later. And (I'm not lying) not a single spot on any of the windows, no matter which windows, or at what side of the house. Well to be honest, there was in all those windows one tiny little spot, apart from that nothing. No matter if they were half sheltered, or fully in the open. Perfect angle to see any spots, in the full sunlight aswell. , I spend 5 minutes examining the windows, nose almost against the window. Examined all the windows aforementioned.
Couldn't believe it.
Now with wfp, when you mix the rain with pure water, the TDS of the rain will be even lower, hence I doubt you'll get spotting anywhere else.
My customers know that I clean in all but the very worst weather conditions, but if they ever comment on it, or object, I'll tell them this story.
I hope we can agree that this was in the very worst conditions possible, and it still didn't make a blind bit of difference. So get out there and clean some windows.