You could be forgiven for scoffing at the fact today is the first full day of the fall season. With temperatures peaking in the low-to-mid-90s this past week, one can still get away with pool attire. The weather pattern is expected to shift to cooler temperatures and become more seasonable after Sunday. Regardless, the seasons don’t always conform to our definitions or expectations. The record-breaking hot summer should be proof of that.
Astronomical fall – what began last night – does have significance, but not in a way that describes our weather patterns. Fall begins with the autumnal equinox, when the axis of the Earth is perfectly upright, so the sun’s rays fall directly on the equator. Fall ends on the winter solstice, when the Northern Hemisphere is tilted away from the sun and nights are at their longest. This year, the winter solstice — and first day of winter — will take place Dec. 21.
The autumnal equinox and the winter solstice do have an effect on the weather. The longest day of the year is in June, so we might expect that the hottest days should also be in June. We know from experience that it tends to come in late July and early August, even as the days are getting shorter.
One of the earth’s most precious resources accounts for the lag. Most of the Earth’s surface is covered by water. Anyone who has experience with a stove knows water takes much longer to heat up than the burner (or your hand). The oceans take longer to absorb and release heat from the sun. This inertia also takes place in the winter, when the coldest temperatures typically happen several weeks after the longest night.
Meteorologists have another, better way of dividing the year. Meteorological fall is probably what you have in mind when you say “fall.” By definition, it includes the entire months of September, October and November.
The journey to fall weather is never a smooth descent, but rather a spirited battle between warm and cold air masses. Like innocent victims, we watch the two duke it out through alternating “Indian summers” and frosty cold snaps.
Like spring, fall is a season of transition and surprises. Hurricanes can spin up well into November, as can tornados. This area’s strongest and most damaging tornado happened shortly after Thanksgiving in 1988. Other times, like in 2007, we languish in extended droughts.
The weather can be warmer or cooler than average and lead to different results. The decision about when to get the sweaters and mittens out is entirely up to you. My good friend from Franklin County begins wearing a fleece once we hit the 80s, whereas I keep some shorts in the drawer throughout the year.
