It's Always Hurricane
Season Somewhere

When is hurricane season, really?

Ask most people when hurricane season is, and they'll name a stretch of late summer and autumn. They're right — for their hemisphere. The Atlantic and the western Pacific are busiest from about August to October. But the Southern Hemisphere's cyclone basins — off Australia, Madagascar, the South Pacific — run their own calendar, and it's half a year out of step. When the north goes quiet, the south is winding up.

Put the two together and a simple question follows: is there ever a moment when the whole planet is quiet? Or does the hand-off between hemispheres keep at least one storm turning somewhere at all times? A platform that already follows every storm can just count and find out — no modeling, no forecasting, only the observed record of where and when storms have actually formed.

The record: 13,547 storms, back to 1842

Every storm is one entry in the TerraPulse tc catalog — a per-cyclone record of its observed track: where it was, when, how strong, and the basin it formed in. The catalog folds together two measured sources: IBTrACS best-track history reaching back to 1842, and live National Hurricane Center fixes for present-day Atlantic and East-Pacific storms. All of it is observed reality — no forecast, no reanalysis, no model output. It holds 13,547 storms across seven basins, led by the western Pacific (4,163) and the south Indian Ocean (2,777).

One honest limit, up front. The number of storms recorded per year roughly doubles across the record — because older storms over the empty stretches of the Southern Ocean were simply never seen, not because the climate changed. That's why this is a study of when storms form, never how many: timing survives an undercounted record; totals don't. Every result below is built on timing.

The two hemispheres run about five months apart

Treating the calendar as a clock face — so December sits next to January — the average Northern Hemisphere storm forms in late August (Aug 29), the average Southern Hemisphere storm in late January or early February (Feb 5). The gap between them is 5.3 months: close to, but not exactly, the clean half-year the "opposite seasons" picture would predict.

What makes this trustworthy is how little it moves when we throw away the unreliable old data. The offset is 5.26 months on the full record, 5.31 from 1970, and 5.32 from 1980 — the undercount of old storms doesn't distort the timing at all. A formal test for "no season" (storms spread evenly through the year) is rejected overwhelmingly in both hemispheres.

It's always hurricane season somewhere

Because the hemispheres alternate, the global storm count never falls to zero. Across the 672 months of the satellite era (1970–2025), not a single one had zero storms active anywhere on Earth. The global cycle bottoms out in May — the Northern season hasn't started, the Southern has wound down — and peaks in September, with the lull running at a fifth to a quarter of the peak. But the floor never touches the ground: even in May, an average of about five tropical cyclones are turning somewhere at any time. And since missing observations can only drop storms from the record, never add them, an undercounted history is if anything biased toward more empty months — so finding none across 56 years is the conservative reading.

The Bay of Bengal's monsoon switches off the strong cyclones

The North Indian basin is famous for a double-peaked season: cyclones before the summer monsoon (peaking in May) and after it (peaking in November), with a deep gap during the monsoon itself. In our raw data that pattern is invisible — all systems together show a broad hump cresting in October — because the monsoon months are filled with weak monsoon depressions the catalog also tracks.

Filter to storms of named strength or above, and the textbook shape snaps into focus: a May peak, a July–August collapse, and a November peak. At hurricane strength the collapse is total — zero hurricane-strength cyclones form in the Bay of Bengal in July or August across the entire record. The monsoon that soaks the subcontinent also shears apart any storm trying to organize over it.

One honest note on scope: intensity was only recorded for about a quarter of North Indian storms (447 of 1,757), and every one of those is from 1972 on. So the double-peak here is a modern, strong-storm pattern — reported as the plain fact that the July–August count is zero, not as a statistical test.

What this says, and what it doesn't

It says: globally, tropical cyclones are a standing feature, not a seasonal one. The Northern and Southern seasons are locked about five months apart, and the hand-off between them keeps at least one storm — usually several — turning somewhere on Earth at every moment of the year. The quietest the planet gets is May, and even then roughly five storms are active.

It does not say anything about whether storms are becoming more frequent, stronger, or shifting their timing. The record's rising storm count is an artifact of better observation, not a climate signal, so we built the whole result around timing, which survives that undercount, rather than totals, which don't. This is a baseline — the measured shape of the planet's storm calendar — against which a standing monitor can later watch for change.

Reproducibility

Every number on this page comes from the results.json file in the hurricane-season-phase workspace. Pipeline: the per-storm table is read from the TerraPulse tc dex (one slot per cyclone, IBTrACS best-track plus live NHC fixes); genesis timing is summarized with circular statistics and a Rayleigh test of the no-season null; the "always a season" claim is an active-storm count over every satellite-era month; and the North Indian double-peak is stratified by measured peak intensity. All inputs are observed storm tracks — no model, forecast, or reanalysis field.