The takeaway
Sotera Health Co shows a pronounced seasonal pattern over 6 years of data — strongest in December (+5.6%) and softest in October (−5.5%).
Right now
In July, the stock has risen 60% of years, averaging +3.8%, about +1.7 pts better than the S&P 500.
The full picture
Sotera Health Co's most dependable month has been December, higher in 5 of 6 years; October has been its least reliable, up just 20% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
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| Median return % | ||||||||||||
| 2025 | ||||||||||||
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| 2022 | ||||||||||||
| 2021 | ||||||||||||
| 2020 | — | — | — | — | — | — | — | — | — | — |
Month by month
The stock's clearest edge over the S&P 500 lands in January (+17.1 pts); it has trailed the market most in September (−11.0 pts).
“vs S&P” is Sotera Health Co’s average for a month minus the S&P 500’s average for that same month — isolating Sotera Health Co’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, December has closed higher 80% of the time versus 83% across the last 6 years — the pattern is holding.
Figures are the typical (median) December return and how often it rose — the last 5 years versus the last 6(the heatmap’s default window). This verdict stays anchored to that 6-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
The seasonal story is really one month's story — December. It has closed higher in 5 of 6 Decembers, a concentration the rest of the calendar can't touch.
Read it with one caveat: the average (+5.6%) runs well ahead of the median (+2.5%), so a handful of outsized years — not steady strength — do much of the lifting. That reliability comes with real swings, mind — even December ranges by 8.7% from year to year, so any single year can land far from the average. Better still, that strength is the stock's own and not just a buoyant market — December has outpaced the S&P 500 by +4.6 points on average. Few peers keep such company in December — the typical stock clears it just 58% of the time.
It doesn't stand entirely alone — July, August, and November have leaned firm as well, if less emphatically. At the other end of the calendar, October has been the soft spot — the weakest of 6 months that average a loss (−5.5%), and the edge isn't year-round — the stock has trailed the S&P 500 in September, October, and March. Its roughest month on record was a −60.1% September in 2022 — a reminder of how hard even a seasonal name can fall.
Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
For a stock this dependable in December, the sharper question is the rest of the year — outside its strong stretch, the calendar gives far less to lean on. With a short 6-year record and returns that swing hard year to year, the signal is best held loosely.
Short answers on the stock's best month (December), its worst (October), and whether it really trades seasonally.
Yes, to a pronounced degree. Since 2020 its best month (December, +5.6%) has run well ahead of its worst (October, −5.5%) — the heatmap above shows how steady that gap has been year to year.
December has been the strongest, averaging +5.6% and closing higher in 5 of 6 years since 2020.
It's the weakest, averaging −5.5% — historically a soft spot, though it still varies from year to year.
Explore
These names have the strongest July track records on record — a starting point for comparison.
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