Inside Bar Teeters on Edge: September Curse Awakening? | SPX Market Briefing | 09 Sept 2025

Yesterday was one of those days that looks boring until you realize it’s setting up something potentially significant. A complete non-mover that eventually developed into a textbook inside day.

We’re still seeing price hover at or near the upper side of the range and kissing the upper Bollinger Band – classic tension building before the next directional commitment.

The overnight futures have already nudged past the inside bar high, which initially looked bullish, but then started to tip over in that ominous way that makes systematic traders pay attention. Should we see the inside bar’s low taken out, this could be the indication we need to see prices tip all the way over into the end of the week.

Everyone knows about the curse of the September sell-off. After this prolonged range dance through August, could we be setting up for the monthly transition that finally breaks the sideways action?

SPX Options = Cashflow Engine.

With this setup? It’s practically an ATM with a checklist.

SPX Market Briefing:

The chart is telling a familiar story with a potentially dramatic twist: range exhaustion meeting seasonal transition right at resistance levels.

Current System Status:

• Inside Day: Completed yesterday with classic range compression

• Position: Upper range boundary + upper Bollinger Band test

• Overnight: Futures nudged above inside bar high, then tipped over

• Systematic Bias: Bearish until proven bullish

• Target Zone: 6400 level as initial systematic objective

Yesterday’s non-moving action might have looked like market indecision, but inside days at resistance levels often precede the most decisive moves. The key now is watching whether the overnight futures’ tip-over behavior follows through with a breach of the inside bar low.

The September Factor: With August firmly behind us and September historically being one of the market’s weakest months, we’re approaching a potential double catalyst. Range completion plus seasonal headwinds could create the perfect setup for systematic bears.

Today’s Systematic Deployment:

Tag ‘n Turn – Currently bearish until proven otherwise. Looking for that move lower to at least the 6400 level, then “we’ll see what we see when we see it.” No point planning beyond the first systematic target until the market shows its hand.

Premium Popper – Waiting for the algo to fire off whatever directional bias emerges from the opening bell.

Lazy Popper – Perfect environment for 0-DTE collection strategies. Whether we break down or reverse higher, the initial direction should provide theta-friendly moves by day’s end.

The beauty of systematic approaches during inside day setups is the clarity: either the range holds and we continue the dance, or it breaks and we get the directional move we’ve been waiting for.

Fun Fact:

Since 1950, September has been the worst performing month for the S&P 500 with an average return of -0.7%, and it’s the only month that has finished positive less than half the time (only 43% positive occurrences). The last four Septembers have been particularly brutal, with declines of 4.9% (2022), 9.3% (2021), 4.8% (2020), and 3.9% (2019).

[Source: Benzinga – “September Market Seasonality: Why This Month Is Historically The Toughest For Investors”]

Trade well,
T2 markets

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