I haven't tried this myself, but may do so if things (ie the weather) don't start to
improve soon.
My hunch is that most customers would be pleased to see you, and for you to do what you reasonably could. Most won't want you to take any unnecessary risks on their property.
I got a new customer today. The patio at the back had decking, covered in a dusting of snow, and it was the customer who told me that she didn't want me to risk going up the ladder on it. Of the two upstairs windows, I was able to do one safely by jamming the ladder under the sill and ensuring that the feet could not slip, but the other was a definite no-no. And I was still given more than my asking price.
John