Session Gaps and Sunday Risk

Forex is often described as a 24-hour market. That is true five days a week. It is not true seven days a week. Between Friday’s close in New York and Sunday’s reopen in Sydney (or Wellington, depending on your broker), the market is closed. During those 65 hours, the world does not stop moving. Central banks meet on weekends occasionally. Geopolitical events happen constantly. Sovereign risk events (elections, referenda, IMF announcements) are often scheduled for Sunday specifically because markets are closed and there is time for participants to digest the news before trading resumes. When the market reopens, the reopen price can be substantially different from Friday’s close. That difference is a gap. If your position was held over the weekend and the gap went the wrong way, your stop loss did not save you.

This article covers the mechanics of session gaps in FX, why they happen, how large they can be, and the specific rules for managing weekend risk. It complements the risk management basics article, which covers standard sizing and stop placement inside an active trading week.

Why FX gaps exist despite being “24-hour”

The 24-hour market description refers to the five weekdays. During those days, when one session closes another opens: Sydney overlaps with Tokyo, Tokyo overlaps with London, London overlaps with New York, New York closes and Sydney is already open. There is no time during the trading week when no venue is quoting the major pairs.

The weekend is different. When New York closes at 5:00 PM ET on Friday, the last active venue for the week shuts down. Sydney and Wellington do not reopen until Sunday at 5:00 PM ET (or 7:00 AM Monday New Zealand time). For approximately 65 hours, the interbank market is closed. Some electronic communication networks continue to accept orders during this window, but the volume is negligible and the prices they show do not represent tradable liquidity.

When the market reopens on Sunday afternoon New York time, the price often gaps. The gap is the difference between the Friday 5:00 PM ET close and the Sunday 5:00 PM ET reopen. In normal weekends, the gap is small: 5 to 15 pips on major pairs, easily absorbed inside the following week’s trading. In eventful weekends, the gap can be much larger: 50 to 200 pips on majors, and multiples of that on emerging-market and exotic pairs.

The gap is not a manipulation or a broker choice. It is the market’s aggregated response to whatever information arrived during the 65 hours the venue was closed. If nothing meaningful happened, the reopen is near the close. If something meaningful happened, the reopen prices in the new information all at once.

What can cause a weekend gap

Six categories of weekend events regularly produce meaningful gaps:

Geopolitical developments. Military escalations, terrorist events, coup attempts, sovereign default announcements. These do not respect the trading calendar. When they occur on a Saturday, the tape prices them in on Sunday reopen.

Central bank surprises. Unscheduled central bank actions are rare but do happen. The Swiss National Bank’s 2015 EUR/CHF floor removal is the canonical extreme (though that was a Thursday, not a weekend). Weekend rate cuts have happened during genuine crises (Fed emergency actions in 2008 and 2020, several ECB and BoE parallel actions).

Elections and referenda. UK general elections, Brexit referendum, US elections, French and German elections, various other sovereign votes. Many are scheduled for Sunday specifically. When results roll in during Sunday evening, the FX reopen prices them.

Weekend policy announcements. G7 or G20 statements, IMF or World Bank announcements, oil-producer group (OPEC+) meetings that occasionally run into weekends, ministerial-level negotiations that conclude Sunday.

Corporate or sovereign credit events. Bank failures, sovereign downgrades, corporate defaults. Rating agencies sometimes publish downgrades after Friday close specifically to give the market time to absorb before Monday.

Natural disasters and pandemic developments. COVID-era weekend gaps were regularly among the largest of any 2020-2021 period. Major earthquakes, tsunamis, or public-health events can drive multi-hundred-pip gaps on affected currencies.

The list above is not exhaustive. The important pattern: eventful weekends produce large gaps; quiet weekends do not. A trader with an open position going into the weekend cannot know which kind of weekend it will be, so the appropriate position management assumes an eventful weekend is possible even when nothing specific is on the calendar.

What a “normal” Sunday open actually looks like

For most weekends, the Sunday open is genuinely quiet. Sydney and Wellington are small venues with limited liquidity. Spreads at 5:00 PM ET Sunday are wide (often two to four times normal weekday spreads on the majors). Volume is thin. The first 30 to 60 minutes of trading typically involves modest price discovery as regional Australian and New Zealand traders start to quote, followed by Tokyo joining at 7:00 PM ET, at which point volume expands materially.

The wide spreads at the reopen matter for position management. A trader whose stop loss triggers during Sunday illiquidity can receive a fill several pips worse than the stated stop price simply because the spread was wider than usual when the stop hit. The slippage glossary entry covers the mechanic. Weekend reopen slippage is typically the worst of any trading day.

Most retail forex brokers do not accept new order entries during the weekend closure. Some accept order modifications (stop and limit adjustments) but do not fill anything. A few brokers accept a limited set of pending orders that go live at Sunday reopen. If your broker allows weekend orders, understand that those orders enter the market during the widest-spread window of the week.

The stop-loss problem over the weekend

The core weekend risk problem: a stop-loss order does not protect you from a gap. If your stop is at 1.1000 on EUR/USD long, and the market reopens Sunday at 1.0900 on some weekend news, your stop fills at approximately 1.0900. The gap was 100 pips beyond the stop. Your loss is 100 pips worse than the sizing math assumed.

This is not a broker bug or a technology failure. Stop orders become market orders when the stop price is touched. If the market has already moved past the stop price by the time it becomes touchable at reopen, the market order fills at the first available price. The next-touch mechanic is the same on Sunday reopen as it is on any other liquidity void.

The implication for risk management: stop losses assume continuous prices. When prices are discontinuous (gaps, weekends, halts), stops fail to bound losses. Sizing that treats a stop-loss as a hard cap is over-sized for any position held through a gap-prone window.

The rules that work

Six rules that professionals use to manage weekend risk. Not all six are applicable to every trading style, but at least two or three should be adopted by any trader who holds positions over weekends.

Rule 1: cut size for weekend-held positions. If your normal per-trade risk is 1 percent of account equity, cut weekend-held positions to 0.5 percent. This is a first-order fix that handles a typical eventful-weekend gap without becoming a serious drawdown.

Rule 2: reduce concurrent positions into the weekend. A trader with five open positions on a Friday afternoon has correlated tail risk across all of them. In an eventful weekend, all five can gap adversely together. Closing two or three of them before the New York close eliminates the compound risk.

Rule 3: check the weekend event calendar. Before Friday close, scan the calendar for scheduled Sunday events: elections, OPEC decisions, G7 or G20 meetings, IMF announcements, central bank speeches at global forums (Jackson Hole, Sintra, IMF spring meetings). If a material event is scheduled, cut size further or close entirely.

Rule 4: understand the pair-specific weekend risk. Yen pairs gap on BoJ, MoF, or Japanese political developments. Sterling pairs gap on UK election or Brexit-related developments. Emerging-market pairs gap on sovereign credit events. The dollar index gaps on US political developments and on any global risk-off shift. Match your weekend exposure to the pair-specific risk profile.

Rule 5: use options for hedging when the risk is meaningful. For traders with the option-market access, buying a weekend hedge (a strangle covering the Sunday reopen window) is a small, quantified cost that caps the tail risk. For traders without options access, the equivalent is closing the position.

Rule 6: accept the possibility of a stopped-out gap. No amount of risk management eliminates gap risk entirely. A position held over the weekend can lose more than the stop-loss math implied. Position size on the assumption that this will occasionally happen; do not size on the assumption that the stop is a hard cap.

The specific Friday-close checklist

Practical operational checklist a trader can run in the 30 minutes before New York close on Friday:

1. Review all open positions. For each: is the position worth carrying through the weekend? What is the expected win contribution against the gap risk?
2. Check the weekend event calendar. Any scheduled event that could produce a gap in a pair you hold?
3. Cut position size on carried trades. Close a portion of each position to reduce weekend risk without abandoning the thesis entirely. Half-position carries are a common compromise.
4. Close any position where the stop distance is large relative to the reasonable weekend gap. A trade with a 60-pip stop in a pair where the reasonable weekend gap is 40 pips is a much different risk profile than the same trade with a 20-pip stop.
5. Note the reopen price expected. If the Sunday reopen prints far from the Friday close, expect widened spreads for the first hour and do not add or manage aggressively during that window.

The checklist takes five minutes and prevents the most common weekend risk mistakes.

The one-sentence summary

Forex is a 24-hour market only five days a week; between Friday New York close and Sunday New York reopen the market is closed and can gap materially on weekend news; stop losses do not protect against gaps because they assume continuous prices, so any position carried through the weekend needs smaller size, tighter concurrency, and a pre-close checklist that assumes an eventful weekend is possible even when the calendar looks quiet.

Related reading: risk management basics covers the standard weekday sizing that this article’s weekend rules modify. Volatility regimes and when to size down covers the broader regime-adaptive sizing framework that weekend risk sits inside. The margin call, what happens covers the far end of the failure mode when a gap combines with over-sized positioning.