Last year, we had our first snow of the season on Sept 15, over a month earlier than normal. Our last snow of "winter" was on May 24th of this year. Normally, we can count on getting our first frost by the end of September and the last one towards the end of May. In recent years, the effects of El Nino and La Nina have changed the normal patterns but last year, neither were a factor. The night time temperatures are already in the upper 40s and dropping, so it appears we're on track for a normal first frost this year. The earlier planting seasons you're experiencing may be a local effect. To the best of my knowledge, the growing season hasn't changed here for a long time.