I live in a rural area, surrounded by fields, farms forests etc. Spiders are a problem all year round.
They get worse in the late summer-early autumn.
The spiders themselves are not too much of a problem, as soon as you wet the window they start abseiling out of the way. Webs too, are easy to deal with.
It’s the spider nests that are the worst, right in the corner of windows and stuck like superglue. Hot water really helps, along with a brisk side-to-side motion with the brush.
My technique is this: clean the frames first, the spider webs will get on the brush, but can easily be brushed off in one clump by just rubbing the brush against the wall. That works best with rendered walls.
Wash the frames, the glass, and the sills. If spiders are anywhere else, then they are left where they are. As someone else rightly said, we’re not in the pest control business.
The worst type of houses for spiders are those with rendered walls and wooden frames.
I’ve no idea why rendered walls seem to attract spiders, maybe their little legs can walk over them more easily. No idea!
But my most important tip is to price them in. It takes extra time dealing with spider webs, make sure to account for them when quoting.