By the time New York traders sit down at their desks, the Asia session has already run its full course and London has been trading for hours. Two complete ranges of price action happened before most American accounts even opened a chart, and both left behind extremes that matter for the rest of the day. Treating the 24-hour cycle as a single flat block misses one of the more useful structures available to an intraday trader: the market runs through three sessions a day, and each one leaves a fresh high and low behind.
The three sessions and what each one leaves behind
The Asia session, roughly 7pm to 4am New York time, is typically the quietest of the three: lower volume, tighter ranges, and a high and low that often get tested and broken once London wakes up. The London session, 3am to noon New York time, does most of forex's real directional work and usually produces the day's widest range on EURUSD and GBPUSD. The New York session, 8am to 5pm New York time, overlaps London for its first few hours and then runs alone through the afternoon, frequently revisiting or extending the levels the earlier two sessions built. Each session's high and low is a real, tradeable level the moment that session ends, and it stays relevant until the next session's range swallows or breaks it.
Using the Asia range as a coiled spring
Because Asia trades quietly, its range often behaves like a compressed spring waiting for London's volume to release it. A EURUSD Asia range from 1.0820 to 1.0840, twenty pips, is a normal, unremarkable box. When London opens, the first meaningful move is frequently a break of one side of that box with real follow-through, and the Asia range then acts the way any broken level does: the side it broke through often turns into support or resistance on a pullback. A trader who marked the Asia high and low before London opened has a level to react to within the session's first hour, rather than discovering the range only after it has already been broken and forgotten.
London's extremes carry into New York
London's high and low are the most consequential of the three because they typically represent the day's real conviction. When New York opens, one of the first useful questions is simple: is price trading above London's high, below London's low, or still inside London's range. Trading above the London high with the New York open showing strength suggests continuation is more likely than reversal. Trading back inside London's range after tagging a new high suggests the move may have been a trap, and the London high behaves like resistance again. On Nasdaq, which runs on the New York cash session primarily, the same logic applies using the prior session's range as the reference rather than London's.
Building the routine
None of this requires extra indicators, just a habit: mark the Asia high and low before London opens, mark London's high and low before New York opens, and know at a glance whether the current session is trading inside, above or below each of the prior ones. On a $10,000 account trading EURUSD, that habit alone often supplies the day's cleanest level: a break of the Asia range at London open, or a rejection at the London high once New York arrives, gives a concrete reason for the trade rather than a guess based on a moving chart.