Even warm weather of early summer was late this year. As a rule, February is considered the end of winter here, but we had a frost in the first part of March, even. People are just now feeling comfortable with planting new stock. Nursery owners must be elated. Not only is there the usual planting of new annuals for summer, but people are having to replace so many plants that it's a buying frenzy.
Seasons are rather moveable feasts anyway.
In days before universal calendars, months and festivals depended entirely on the weather. Summer came when it got warm enough to take animals that had overwintered in shelters out to far pastures and leave them there. This led to the organized celebration of Bealtainn, the first day of summer, later called May Day. Next month will come in with May Day. May Day in Michigan, where I lived most of my life, was not summer.