The takeaway
SPDR® Bloomberg 1-3 Month T-Bill ETF shows a slight seasonal lean over 10 years of data — strongest in August (+0.2%) and softest in April (+0.1%).
Right now
In July, the fund has risen 80% of years, averaging +0.2%, roughly 2.0 pts behind the S&P 500.
The full picture
SPDR® Bloomberg 1-3 Month T-Bill ETF's most dependable month has been August, higher in 9 of 10 years; April has been its least reliable, up just 70% of the time.
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Month by month
Across the year the fund has stayed close to the S&P 500 — no single month stands out as a real edge.
“vs S&P” is SPDR® Bloomberg 1-3 Month T-Bill ETF’s average for a month minus the S&P 500’s average for that same month — isolating SPDR® Bloomberg 1-3 Month T-Bill ETF’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, August has closed higher 80% of the time versus 90% across the last 10 years — the pattern is holding.
Figures are the typical (median) August 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
Dependability is the through-line here. August stands out, higher in 9 of 10 Augusts, but it heads a clutch of months that pull the year reliably upward.
Its average (+0.2%) and median (+0.1%) 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. At the other end of the calendar, April 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.
Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
The takeaway is less about when to buy than what to expect: August aside, the fund's months offer little reliable tilt.
Short answers on the fund's best month (August), its worst (April), and whether it really trades seasonally.
Only mildly. The fund's months are fairly even — August is the firmest (+0.2%) and April the softest (+0.1%), a narrow spread that points to weak seasonality rather than a strong calendar effect.
August has been the strongest, averaging +0.2% and closing higher in 9 of 10 years since 2016.
It's the weakest month, but it has still averaged a small gain (+0.1%) — quiet rather than genuinely bad.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade