Looking ahead to the rainy weather I was thinking about a cycling helmet cover but they all seem to just cover the helmet, so allowing the rain to run down the back of your neck.
What solutions have people found?
Helmet covers are ok for when you don't want to pack a lot of gear, don't want to get your head wet, and/or the risk of rain is low. But yes ... rain can run down your neck.
If you know you want more hardcore weather protection, you probably want to be looking at a jacket with a hood! Fortunately, dedicated bike wear already exists from many manufacturers that can give a number of advantages, specific to cyclists like good breathability, extended tails for butt protection! reflective details for night riding etc.
As an example, I'd be looking at the Altura Nightvision Jackets. Offerings from Endura, Scott etc.
Some of the Altura jackets have removable hoods. If used, these are generally worn underneath your helmet. The hoods are fairly small and light and fit easily into one of the numerous pockets of the jacket when not in use.
Other Jackets are more MTB focused, and these can have oversized hoods that actually fit OVER your helmet. The ones I've seen are usually fixed and they might be referred to sometimes as 'grown hoods' or something like that.
While you can use more generic clothing, I personally have found that the advantages of cycle specific clothing are worth going for these options.