How cold does it actually feel there?

My friends and I are visiting Iceland next week and are kinda stressing about what to pack. I check the weather and low 50’s seems doable but also maybe like it’s a lie haha

Please keep in mind, I’m also a baby from California where it rarely gets cold. (I had to buy a jacket for this trip)

I know to pack waterproof options and do layers but any insight on October weather or current weather (anyone there now?) would be amazing! TIA!