The takeaway
US Treasury 6 Month Bill ETF shows a slight seasonal lean over 3 years of data — strongest in August (+0.4%) and softest in May (+0.3%).
Right now
In July, the fund has risen 100% of years, averaging +0.4%, roughly 1.8 pts behind the S&P 500.
The full picture
US Treasury 6 Month Bill ETF's most dependable month has been August, higher in 3 of 3 years; May has been its least reliable, up just 100% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Win rate % | ||||||||||||
| Median return % | ||||||||||||
| 2025 | ||||||||||||
| 2024 | ||||||||||||
| 2023 | — | — |
Month by month
The fund's clearest edge over the S&P 500 lands in February (+0.6 pts); it has trailed the market most in November (−2.0 pts).
“vs S&P” is US Treasury 6 Month Bill ETF’s average for a month minus the S&P 500’s average for that same month — isolating US Treasury 6 Month Bill ETF’s own seasonal edge from broad market drift.
Reality check
Over the last 3 years, August has closed higher 100% of the time versus 100% across the last 3 years — the pattern is holding.
Figures are the typical (median) August return and how often it rose — the last 3 years versus the last 3(the heatmap’s default window). This verdict stays anchored to that 3-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
Dependability is the through-line here. August stands out, higher in all 3 Augusts, but it heads a clutch of months that pull the year reliably upward.
Its average (+0.4%) and median (+0.5%) land within a hair of each other — the tell of steady, year-after-year gains rather than one outlier doing the work. Set against the S&P 500, mind, August is close to a wash — the gain mirrors the market more than it beats it. That consistency sets it apart from the field, where the average stock manages August only about 52% of the time.
The lift is near-universal — strength runs through almost every month of the year, not one window. On the other side of the ledger, May is the year's quietest corner, essentially flat on average, and the edge isn't year-round — the fund has trailed the S&P 500 in November, July, and April.
The takeaway is less about when to buy than what to expect: August aside, the fund's months offer little reliable tilt. With a short 3-year record, the signal is best held loosely.
Short answers on the fund's best month (August), its worst (May), and whether it really trades seasonally.
Only mildly. The fund's months are fairly even — August is the firmest (+0.4%) and May the softest (+0.3%), a narrow spread that points to weak seasonality rather than a strong calendar effect.
August has been the strongest, averaging +0.4% and closing higher in all 3 years on record since 2023.
It's the weakest month, but it has still averaged a small gain (+0.3%) — quiet rather than genuinely bad.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade