it;s still cold on the early spring.为什么用“on”?

it;s still cold on the early spring.为什么用“on”? it's cold outside .you should (put on )your coat 为什么put on 用 it is on a cold moring为什么用on It's cold,you'd better put on the s_____ it's difficult to get the car_________ on cold morinigs We still went on working ______ cold it was. Do you still get up early on the weekend Still,he shouted as he ___ on the cold sidewalk it's on the Is it cold on in Spring on the Spring on Spring in the Spring It's cold here.-------- I switch on the heating?A.Should B.S