Chicakō
@chicago-seasons.bsky.social
An interpretation of the traditional division of the year into 72 microseasons or kō (候), for the climate in Chicago, by u/sherrillo on Reddit: https://docs.google.com/spreadsheets/d/12uh4lpcqnkYuDY75r7HwKpKLtrefyALw (bot run by @maeveynot.bsky.social)
Dec 22–31: Deep‑freeze windows
Arctic shots consolidate shelf ice and stiffen soils; the city settles into true winter.
Arctic shots consolidate shelf ice and stiffen soils; the city settles into true winter.
December 22, 2025 at 2:04 PM
Dec 22–31: Deep‑freeze windows
Arctic shots consolidate shelf ice and stiffen soils; the city settles into true winter.
Arctic shots consolidate shelf ice and stiffen soils; the city settles into true winter.
Dec 17–21: Solstice sun dogs
Low sun angles and ice crystals produce halos and sun dogs on the coldest mornings.
Low sun angles and ice crystals produce halos and sun dogs on the coldest mornings.
December 17, 2025 at 1:53 PM
Dec 17–21: Solstice sun dogs
Low sun angles and ice crystals produce halos and sun dogs on the coldest mornings.
Low sun angles and ice crystals produce halos and sun dogs on the coldest mornings.
Dec 12–16: Winter ducks on open water
Goldeneye and mergansers sparkle on Lake Michigan and larger lagoons.
Goldeneye and mergansers sparkle on Lake Michigan and larger lagoons.
December 12, 2025 at 2:27 PM
Dec 12–16: Winter ducks on open water
Goldeneye and mergansers sparkle on Lake Michigan and larger lagoons.
Goldeneye and mergansers sparkle on Lake Michigan and larger lagoons.
Dec 7–11: Owl courtship begins
Great horned owls become more vocal as courtship ramps up heading into winter.
Great horned owls become more vocal as courtship ramps up heading into winter.
December 7, 2025 at 1:30 PM
Dec 7–11: Owl courtship begins
Great horned owls become more vocal as courtship ramps up heading into winter.
Great horned owls become more vocal as courtship ramps up heading into winter.
Dec 2–6: Harbor skim ice
Protected harbors and ponds glaze over on calm, cold nights before breaking by afternoon sun.
Protected harbors and ponds glaze over on calm, cold nights before breaking by afternoon sun.
December 2, 2025 at 2:01 PM
Dec 2–6: Harbor skim ice
Protected harbors and ponds glaze over on calm, cold nights before breaking by afternoon sun.
Protected harbors and ponds glaze over on calm, cold nights before breaking by afternoon sun.
Nov 27–Dec 1: First measurable snow (typ.)
Many years see the first measurable snowfall in this window, though it varies widely.
Many years see the first measurable snowfall in this window, though it varies widely.
November 27, 2025 at 1:57 PM
Nov 27–Dec 1: First measurable snow (typ.)
Many years see the first measurable snowfall in this window, though it varies widely.
Many years see the first measurable snowfall in this window, though it varies widely.
Nov 22–26: Final acorn frenzy
Squirrels finish caching acorns and walnuts; gnawed shells litter stump tops.
Squirrels finish caching acorns and walnuts; gnawed shells litter stump tops.
November 22, 2025 at 2:43 PM
Nov 22–26: Final acorn frenzy
Squirrels finish caching acorns and walnuts; gnawed shells litter stump tops.
Squirrels finish caching acorns and walnuts; gnawed shells litter stump tops.
Nov 17–21: Lake‑effect ceilings
Persistent gray stratus and drizzle develop under cold NE winds off the lake.
Persistent gray stratus and drizzle develop under cold NE winds off the lake.
November 17, 2025 at 2:03 PM
Nov 17–21: Lake‑effect ceilings
Persistent gray stratus and drizzle develop under cold NE winds off the lake.
Persistent gray stratus and drizzle develop under cold NE winds off the lake.
Nov 12–16: Ginkgo gold drop
Ginkgoes often shed en masse after the season’s first sharp cold night—sidewalks turn gold.
Ginkgoes often shed en masse after the season’s first sharp cold night—sidewalks turn gold.
November 12, 2025 at 2:26 PM
Nov 12–16: Ginkgo gold drop
Ginkgoes often shed en masse after the season’s first sharp cold night—sidewalks turn gold.
Ginkgoes often shed en masse after the season’s first sharp cold night—sidewalks turn gold.
Nov 7–11: Waterfowl highways
Diving ducks, geese, and swans stage on open water along the lakefront and lagoons.
Diving ducks, geese, and swans stage on open water along the lakefront and lagoons.
November 7, 2025 at 1:38 PM
Nov 7–11: Waterfowl highways
Diving ducks, geese, and swans stage on open water along the lakefront and lagoons.
Diving ducks, geese, and swans stage on open water along the lakefront and lagoons.
Nov 2–6: First flurries
Cold rain mixes with snow; brief bursts whiten grass before melting.
Cold rain mixes with snow; brief bursts whiten grass before melting.
November 2, 2025 at 1:45 PM
Nov 2–6: First flurries
Cold rain mixes with snow; brief bursts whiten grass before melting.
Cold rain mixes with snow; brief bursts whiten grass before melting.
Oct 28–Nov 1: Leaf‑fall lanes
Windy days send leaves streaming; piles gather along curbs and fences.
Windy days send leaves streaming; piles gather along curbs and fences.
October 28, 2025 at 12:37 PM
Oct 28–Nov 1: Leaf‑fall lanes
Windy days send leaves streaming; piles gather along curbs and fences.
Windy days send leaves streaming; piles gather along curbs and fences.
Oct 23–27: Color peak drifts cityward
Best urban color often arrives late Oct into early Nov, with oaks lagging.
Best urban color often arrives late Oct into early Nov, with oaks lagging.
October 23, 2025 at 1:32 PM
Oct 23–27: Color peak drifts cityward
Best urban color often arrives late Oct into early Nov, with oaks lagging.
Best urban color often arrives late Oct into early Nov, with oaks lagging.
Oct 18–22: First freeze (typ.)
Average first freeze near this window; tender annuals blacken overnight.
Average first freeze near this window; tender annuals blacken overnight.
October 18, 2025 at 12:29 PM
Oct 18–22: First freeze (typ.)
Average first freeze near this window; tender annuals blacken overnight.
Average first freeze near this window; tender annuals blacken overnight.
Oct 13–17: Maples start to flame
Norway and red maples shift through oranges and reds; sugar maples glow in preserves.
Norway and red maples shift through oranges and reds; sugar maples glow in preserves.
October 13, 2025 at 12:47 PM
Oct 13–17: Maples start to flame
Norway and red maples shift through oranges and reds; sugar maples glow in preserves.
Norway and red maples shift through oranges and reds; sugar maples glow in preserves.
Oct 8–12: Frost watch
Patchy frost appears in low spots; gardeners cover late tomatoes and peppers.
Patchy frost appears in low spots; gardeners cover late tomatoes and peppers.
October 8, 2025 at 12:55 PM
Oct 8–12: Frost watch
Patchy frost appears in low spots; gardeners cover late tomatoes and peppers.
Patchy frost appears in low spots; gardeners cover late tomatoes and peppers.
Oct 3–7: Ragweed’s last stand
Ragweed remains troublesome until the first hard frost knocks it back.
Ragweed remains troublesome until the first hard frost knocks it back.
October 3, 2025 at 12:23 PM
Oct 3–7: Ragweed’s last stand
Ragweed remains troublesome until the first hard frost knocks it back.
Ragweed remains troublesome until the first hard frost knocks it back.
Sep 28–Oct 2: Goldenrod finale
Late species carry the banner as others fade; pollinator traffic remains high on warm days.
Late species carry the banner as others fade; pollinator traffic remains high on warm days.
September 28, 2025 at 12:19 PM
Sep 28–Oct 2: Goldenrod finale
Late species carry the banner as others fade; pollinator traffic remains high on warm days.
Late species carry the banner as others fade; pollinator traffic remains high on warm days.
Sep 23–27: Hummers on the wing
Ruby‑throated hummingbirds tank up at salvias and feeders; most depart by early October.
Ruby‑throated hummingbirds tank up at salvias and feeders; most depart by early October.
September 23, 2025 at 1:00 PM
Sep 23–27: Hummers on the wing
Ruby‑throated hummingbirds tank up at salvias and feeders; most depart by early October.
Ruby‑throated hummingbirds tank up at salvias and feeders; most depart by early October.
Sep 18–22: Equinox balance
Day and night nearly equal; first cool snaps nudge trees toward change.
Day and night nearly equal; first cool snaps nudge trees toward change.
September 18, 2025 at 1:40 PM
Sep 18–22: Equinox balance
Day and night nearly equal; first cool snaps nudge trees toward change.
Day and night nearly equal; first cool snaps nudge trees toward change.