|Maggie and Lucy demonstrating my point nicely.|
While I would never keep my cats from sitting in the windows, allowing them to do so means allowing them to take some risks. Cats can be seriously injured by sitting in improperly prepared open windows, so cat owners would do well to take a few precautions.
For starters, make sure that any cords attached to blinds or curtains are securely attached to the wall. I learned this lesson the hard way when Eamon got tangled in my blind pulls a few years ago. Thankfully, I was only gone for a few minutes and he lived to tell the tale, but the cat was terrified and bit me quite seriously as I was trying to get him untangled. I have scars to remind me of that day. Anyway, I use plain coat hooks for my cords. I wrap the cords around the hooks, well out of the reach of the cats, and I unwind the cords when I want to lower the blinds again. It's really the best way to keep your cats safe.
Next, windows that open horizontally, as shown in this picture, can have special dangers. My cats bump and nudge the windows when they're trying to get comfortable, and loose windows could easily slam shut and squash their poor heads or backs. About 90 percent of my windows are sticky and don't budge, but those that do move, I prop open on both sides with dowels.
Finally, cats seem to like to sleep pushed up against the screen. Loose screens could lead to major falls, and contrary to popular belief, cats will not survive all falls from great heights. Cats that do survive may have broken bones, or they may simply run away after a fall. Each spring, I test the screens to make sure they're secure in the frames. If they're not, I fix them.
Opening the windows for the cats is a great idea, but just make sure you do so safely.