Why did you tell listeners that summer starts June 1, when in fact it starts June 21!

Dear Tom,
Why did you tell listeners that summer starts June 1, when in fact it starts June 21!
— Cheryl Bolingbrook
Dear Cheryl,
While astronomical seasons are absolute, defined by the spring and fall equinoxes and the summer and winter solstices, the beginning and end times and dates of the four seasons can vary by days from year to year. This year, astronomical summer will begin at 5:07 a.m. June 21. That variance is why meteorologists prefer to use four three-month meteorological seasons. In the Northern Hemisphere, June, July and August define meteorological summer, while meteorological winter consists of December, January and February. The remaining six months define meteorological spring and fall. Since climate records are kept on a monthly basis, defining a season in terms of three complete months makes comparisons and rankings a relatively easy task.