Cedar fever: the pollen season that happens in winter

What's actually happening

"Cedar" here is Ashe juniper, which blankets millions of acres of the Hill Country. Unlike almost every other allergenic tree in North America, it pollinates in the dead of winter — and it doesn't trickle. Cold fronts crack the pollen cones open all at once, sending up clouds thick enough to look like smoke rising off the hills. On the season's biggest days, pollen rides southwest winds far beyond the Hill Country itself.

Related junipers run their own, milder late-winter seasons elsewhere — eastern red cedar through Oklahoma and the southern Plains in late winter, and juniper across the high deserts — but the December–February spectacle is a Texas phenomenon.

Cedar country calendars

The full Texas pollen year — cedar, oak, the fall cedar elm season, and ragweed — is on the Texas page, with city detail for the heart of the cedar belt:

• Austin
• San Antonio
• Waco

Common questions

When is cedar fever season in Texas?

Mountain cedar typically begins releasing pollen in mid-December, builds to a peak in mid-January, and tapers off toward the beginning of March. The worst of it — the stretch Texans mean by "cedar fever season" — is mid-December through February.

Where is cedar fever worst?

The Hill Country west of Interstate 35 — the Austin and San Antonio corridor — sits in the thickest Ashe juniper country in the world, and southwest winds carry the pollen across much of the state.

Why does it happen in winter?

Mountain cedar is the rare tree that pollinates in winter. Passing cold fronts — dry, windy, with fast pressure swings — pop the pollen cones open, so the biggest days often follow a front. Almost nothing else is pollinating then, which is how a single species earned its own season.