Average Earth's surface temperature all the way around each latitude, then watch that profile change month by month. The warmest band marches north in summer and south in winter, chasing the overhead sun across forty-odd degrees. But it never settles on the equator — not even at the equinox. The thermal equator's true home is a few degrees north, and that permanent tilt is the planet's own lopsided geography: more land up top, holding more heat.
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permanent home of the hottest band (annual mean)
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how far it wanders north to south
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summer extreme (july peak)
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winter extreme (january peak)
Loading one year of the planet's temperature…
ZONAL-MEAN TEMPERATURE · —peak at —
WHERE THE PEAK SITS, MONTH BY MONTH
The peak's yearly path. The dashed line is its annual mean — the permanent thermal equator. It rides north of zero all year because the curve spends more of itself above the line than below.
The sun's overhead point swings between the two tropics each year, and the warmest latitude band follows it — but at a lag, and never symmetrically. In summer it climbs to its northern extreme; in winter it retreats south, yet the southern retreat falls short of the northern reach. Run the year and the asymmetry is plain: the peak lingers in the north.
Subtract the seasons — average the peak's position over all twelve months — and it still lands north of the equator. That residue is not weather; it is the shape of the planet. The Northern Hemisphere carries far more land, and land heats faster and harder than the ocean it displaces; ocean currents also ferry heat across the equator heading north. So even at the equinoxes, when the sun stands over the equator itself, the hottest band of Earth is already a few degrees up. The season moves it. The geography keeps it.
How this was built. One year of Open-Meteo's ERA5 archive — daily mean 2 m air temperature. For each month, a mid-month window is sampled on a grid of 35 latitude bands (85°S→85°N, every 5°) across 12 longitudes, then averaged around each latitude to give that month's zonal-mean profile. The peak latitude is located by fitting a parabola to the warmest band and its two neighbours, so it resolves finer than the 5° grid. "Permanent" = the mean of the twelve monthly peaks; "swing" = northernmost minus southernmost. The drag scrubber interpolates linearly between adjacent months. Land/ocean heat-capacity asymmetry and cross-equatorial ocean heat transport are the established cause of the year-round northern offset.
The PloverData: ERA5 via Open-Meteo · No build step · Source on request