The takeaway
Guardant Health Inc shows a pronounced seasonal pattern over 8 years of data — strongest in June (+7.7%) and softest in September (−3.9%).
Right now
In July, the stock has risen 71% of years, averaging +3.6%, about +1.5 pts better than the S&P 500.
The full picture
Guardant Health Inc's most dependable month has been June, higher in 6 of 7 years; September has been its least reliable, up just 29% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
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| 2018 | — | — | — | — | — | — | — | — | — |
Month by month
The stock's clearest edge over the S&P 500 lands in August (+8.6 pts); it has trailed the market most in December (−9.2 pts).
“vs S&P” is Guardant Health Inc’s average for a month minus the S&P 500’s average for that same month — isolating Guardant Health Inc’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, June has closed higher 100% of the time versus 86% across the last 8 years — the pattern is strengthening.
Figures are the typical (median) June return and how often it rose — the last 5 years versus the last 8(the heatmap’s default window). This verdict stays anchored to that 8-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
Strip the year back and a single month does the heavy lifting: June, up in 6 of 7 Junes while the other eleven tend to blur together.
A typical June brings +5.4%, a shade under the +7.7% average. It is also the calendar's calmest month, its returns swinging least from year to year (a 9.1% spread), and even its worst June in 8 years lost only 8.2% — the gentlest downside anywhere on its calendar. Crucially, the gain is the stock's own rather than a rising tide's: June has cleared the S&P 500 by +7.5 points above the index. That consistency sets it apart from the field, where the average stock manages June only about 52% of the time.
The strength clusters rather than stands alone — June–August forms a firm stretch that carries much of the year. On the other side of the ledger, September has been the soft spot — the weakest of 4 months that average a loss (−3.9%), and the edge isn't year-round — the stock has trailed the S&P 500 in December, September, and April. Its roughest month on record was a −48.1% December in 2022 — a reminder of how hard even a seasonal name can fall.
June has now closed higher 5 years running. If anything it has sharpened recently — the last five Junes run ahead of the earlier years.
The takeaway is less about when to buy than what to expect: June aside, the stock's months offer little reliable tilt. With a short 8-year record and 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 2018 its best month (June, +7.7%) has run well ahead of its worst (September, −3.9%) — the heatmap above shows how steady that gap has been year to year.
June has been the strongest, averaging +7.7% and closing higher in 6 of 7 years since 2018.
It's the weakest, averaging −3.9% — 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