Microseason 52 of 72 · September 16–20
Equinox — dark overtakes light
A five-day window of the year, read through nine North American climate regions.
Same week, nine climates
A microseason names a five-day window of the solar year. What that window actually looks like on the ground depends on where you are. Below, the same calendar window read through each of nine North American climate regions.
- NENortheast Continental
Equinox — dark overtakes light
Autumnal equinox — nights will now outpace the days.
- SESoutheast Subtropical
Day and dark find balance
Autumnal equinox: day and night equal. Swallows depart in waves; darkness begins its long expansion over the South.
- PNWPacific Northwest
Equinox—darkness gains
Day and night balance. Darkness now outpaces light by hours each following week. The forest's rhythm shifts toward dormancy.
- CACalifornia Mediterranean
Equinox descent
Day and night balance. Autumn officially arrives; Pacific high weakens slightly northward.
- MWMountain West
Equinox: darkness claims the high passes
Autumnal equinox arrives; day and night equal, but the rate of darkness gain accelerates toward winter solstice.
- MPPlains Continental
Equinox brings balance to day
Autumnal equinox: day and night equal length. Hawk migration continues. Swallows depart for South America. The prairie takes on an amber light as the sun angles lower.
- SWSouthwest Desert
Equinox evening shadow
Day and night equal; darkness overtakes daylight as the axis tilts away.
- TRTropical / Sub-Tropical
Equinox approaches
Days shorten perceptibly as the autumnal equinox nears; afternoon shadows lengthen across mangrove flats.
- AKAlaska Subarctic
Aurora blazes every clear night
Autumn equinox passed; darkness now longer than light. Aurora borealis dances nightly across star-studded skies.
About the 72-microseason calendar
A microseason is a five-day window of the solar year — long enough to notice something change, short enough that the change is specific. The year holds seventy-two of them, six per month, ordered by what the natural world is doing rather than what the clock says. Almanac calendars like this are an old American habit, kept by farmers, gardeners, and birders for centuries; Weather Story collects them into a single reference.
Each microseason is read through nine North American climate regions. The phenological events that mark a five-day window vary with ecology — the strawberries that open in the Northeast might coincide with the first magnolias dropping in the Southeast and the salmonberry blossoms unfurling in the Pacific Northwest. Same week, nine ecologies, nine readings.