Warmer days are here again and the mercury is rising slowly. But Cambridge’s clime is anything but predictable. Spring may be for shedding layers, but once the coat comes off, it’s often toted around anyway. The weather usually doesn’t make up its mind until June, but that doesn’t mean fashion falls by the wayside — it just makes for smarter dressers, with preparedness flirting with flair. Students making the most of the outdoors and Harvard’s Common Spaces demonstrated this again and again, with notable spring trends a contrasting mix of minis and knits, lace and leather, floral and boots, and pops of color — but not too much.