If you play with Seasons installed, umbrellas are way more useful than they first appear. Spring and fall come with a lot of rain, and Sims who get caught outside without an umbrella usually end up feeling uncomfortable. Sims who hate being outdoors can even get angry about it, which quickly snowballs into a bad day.
Umbrellas also pull double duty for vampire Sims. Until they unlock sun resistance, an umbrella is one of the few ways they can safely go outside during the day without risking serious damage.
It's honestly super easy, just needs Seasons to be installed. Build Mode > Appliances > Miscellaneous Appliances, and you'll find the Umbrella Rack there. I'd put it somewhere you'll actually pass by, like near the front door or in the hallway. Fastest way to find it though? Just type "umbrella" straight into the Build Mode search bar and it pops right up. Once it's placed, click it, grab an umbrella, done.
Good news, it's cheap — only 100 Simoleons, and just the one rack covers your entire household since every Sim can grab their own umbrella from it. There's a decent variety of styles too, so you can actually match it to your Sim's fit or vibe instead of everyone carrying the same boring one. One thing worth flagging though: umbrellas do NOT protect against lightning. If a storm rolls in, get your Sim inside immediately. That Scared by Thunderstorm moodlet popping up is basically the game telling you to get indoors, so don't ignore it.