The takeaway
Ultragenyx shows a pronounced seasonal pattern over 10 years of data — strongest in June (+2.7%) and softest in September (−6.0%).
Right now
In July, the stock has fallen 40% of years, averaging −3.7%, roughly 5.9 pts behind the S&P 500.
The full picture
Ultragenyx's most dependable month has been June, higher in 6 of 10 years; September has been its least reliable, up just 10% of the time.
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Month by month
The stock's clearest edge over the S&P 500 lands in February (+4.4 pts); it has trailed the market most in March (−10.0 pts).
“vs S&P” is Ultragenyx’s average for a month minus the S&P 500’s average for that same month — isolating Ultragenyx’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, June has closed higher 40% of the time versus 60% across the last 10 years — the pattern is weakening.
Figures are the typical (median) June return and how often it rose — the last 5 years versus the last 10(the heatmap’s default window). This verdict stays anchored to that 10-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
There's a real but measured seasonal tilt here, toward June — the firmest corner of the calendar, higher in 6 of 10 Junes.
The strength looks broad-based rather than freakish: its average (+2.7%) and median (+2.4%) sit close together, so no single blow-out year is flattering the figure. That reliability comes with real swings, mind — even June ranges by 14.9% 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 — June has outpaced the S&P 500 by +2.5 points on average.
It doesn't stand entirely alone — January and August have leaned firm as well, if less emphatically. The weaker half of the year is plainer: September has been the soft spot — the weakest of 6 months that average a loss (−6.0%), and the edge isn't year-round — the stock has trailed the S&P 500 in March, October, and July. Its roughest month on record was a −44.9% January in 2016 — a reminder of how hard even a seasonal name can fall.
The pattern has softened of late, June's last five years slipping below its longer-run record.
Treat it as a tendency rather than a rule — seasonality describes the past, not a promise. With returns that swing hard year to year, the signal is best held loosely.
Short answers on the stock's best month (June), its worst (September), and whether it really trades seasonally.
Yes, to a pronounced degree. Since 2016 its best month (June, +2.7%) has run well ahead of its worst (September, −6.0%) — the heatmap above shows how steady that gap has been year to year.
June has been the strongest, averaging +2.7% and closing higher in 6 of 10 years since 2016.
It's the weakest, averaging −6.0% — 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.
Before you trade