For me, it depends mostly on the weather, but also the month of the year.
If it is summer, the first cool day in September I feel like summer is over. It might only be a day, and then heat up again, but I’m so dreading the coming cold weather that with the cool day I will have declared summer being over, and fall officially beginning. Fall also needs the leaves turning colors.
It’s similar with winter, either some snow or a really cold day, plus if most of the leaves have fallen, and I’ll state winter has begun. There almost always is an Indian summer day of two (is it ok to still call it that?) but I know it’s really winter.
Growing up my mom used to say once we pay taxes (April 15) it doesn’t s is anymore. That of course depends where you live. It was true where I grew up, but not where I went to school.
Spring, you see things blooming, and the warm days start. I do kind of use the fashion rule about not wearing white until after Easter.
I mentioned above that it’s mostly the weather for me. The other part, the month, what I mean is if it wasn’t is January, and I usually warm, I’m still going to call it winter, it’s a warm winter. In Florida it’s not unusual to have “spring-like” weather through the winter months. In Florida we tend to use two seasons, summer and winter, but we have spring weather for almost 8 months. I don’t typically use the term fall in FL because we don’t have many trees that turn color or lose leaves.