Microseason 20 of 72 · April 6–10
Warblers appear in the understory
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
Warblers appear in the understory
First warblers arrive — Yellow-rumped, Palm, Pine lead the wave.
- SESoutheast Subtropical
Barn swallows carve the warming sky
Barn swallows return en masse. Cardinals sing in full voice. The forest fills with breeding calls.
- PNWPacific Northwest
Swallows Arrive at the Bridges
Barn swallows return to eaves and bridge abutments; cliff swallows scout nesting ledges. Warblers flood the canopy—orangecrowned, black-capped—insect-gleaning through emerging leaves.
- CACalifornia Mediterranean
Warblers flood the understory
Migrating songbirds peak—Nashville, Townsend's, and orange-crowned warblers fill oak canopies. Pacific coast skies clear to azure.
- MWMountain West
Swallows and swifts slice the warming sky
Violet-green swallows and Cliff swallows return to canyon walls and ridges. Insect hatches from snowmelt streams accelerate.
- MPPlains Continental
Cliff Swallows Return to Mud Nests
Swallows and barn swallows arrive to rebuild mud nests on cliffs, bridges, and building eaves; insect trapping begins.
- SWSouthwest Desert
Brittlebush carpets the desert floor
Brittlebush blooms golden across the bajadas; saguaro buds tighten at the arms of the giants; lesser nighthawks return at dusk.
- TRTropical / Sub-Tropical
Migrants pour southward
Warblers descend into mangrove thickets and hammock understories on their way south, filling dawn air with song.
- AKAlaska Subarctic
Northern birds navigate by starlight
Tundra swans and geese flood through the Yukon-Kuskokwim delta; warblers appear. Daylight extends to 14+ hours in Anchorage.
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.