All this talk about its being spring brought back some memories. When my son was about 3 or 4, he heard on the radio or TV that spring had begun. It was a year very similar to this one.
He was convinced that since it was spring, he should stop wearing his winter clothes and begged me to get out his "spring" clothes. He was very fussy about his appearance and wouldn't budge - he wanted his spring clothes. I remembered my mother's solution to a stubborn child so I gave in. The house was warm enough for short sleeves, so I really didn't see the harm.
After a day or two, he relented and went back to the long sleeve shirts and comfort.
My mother's solution? When my brother was about 3 years old, all he wanted to eat was Campbell's Chicken Noodle soup - for every meal. She gave in to him. He had that soup for breakfast, lunch and supper for two days. At last, he asked if he could please have something besides chicken noodle soup. Problem solved.
One of the things to remember when dealing with children is to pick your battles. As long as what they are pushing for won't hurt them and doesn't contradict your core beliefs, why not let them have what they want. Put your foot down when they get really outlandish ideas.