Why Idaho Has Two Time Zones—and Where the Hour Changes
Idaho uses Mountain and Pacific Time. Boise and much of southern Idaho follow Mountain Time; Coeur d’Alene, Moscow and Lewiston follow Pacific Time. The Salmon River forms part of the boundary, including near Riggins.
Idaho has two time zones, and the boundary is more interesting than a straight line on a map. Federal rules trace it partly along the Salmon River, creating a one-hour difference between much of northern and southern Idaho.
Knowing where that change occurs is useful for road trips, event planning and calls between communities.
One state, two clocks
Idaho is divided between Mountain and Pacific time. Boise, Twin Falls, Idaho Falls and much of southern Idaho observe Mountain Time, while Coeur d'Alene, Moscow and Lewiston follow Pacific Time. That means a call scheduled for 9 a.m. in Boise reaches someone in Coeur d'Alene at 8 a.m.
Both regions observe daylight saving time, so the usual one-hour difference persists through the seasonal clock changes. For statewide meetings, school travel and events, specifying the time zone is more reliable than writing a clock time alone.
Why the Salmon River matters
The dividing line is established by federal regulation, not merely local custom. Under 49 CFR 71.9, the boundary runs along the Idaho–Montana border, follows the Idaho County–Lemhi County boundary to the Salmon River, and then follows the river west to Oregon.
This makes Idaho County unusual: portions north of the Salmon River use Pacific Time, while the portion south of the river uses Mountain Time. The rule also specifies that municipalities located on the described boundary are assigned Mountain standard time.
The crossing near Riggins
U.S. Highway 95 crosses the Salmon River near Riggins, where the crossing is commonly called the Time Zone Bridge. Idaho Fish and Game uses the 'SH95 Timezone Bridge' as a named landmark in its river-section descriptions.
For a driver, the important point is that the time-zone boundary follows the river rather than a county line everywhere. A navigation app or phone may adjust automatically, but printed event schedules, appointments and business hours may not.
What travelers should check
If you are driving between Boise and northern Idaho, remember that travel time and arrival time are different calculations. A journey can take several hours while the destination clock is one hour earlier. On the return trip, the clock moves forward again.
Before a trip, confirm the destination's local time, especially for lodging check-in, reservations, guided activities or scheduled closures. Idaho's statewide agencies sometimes label regional information by time zone; Idaho Fish and Game, for example, explicitly separates Pacific and Mountain Time areas in its published materials.
The rule behind the map
The split is not a recent change. Federal law specifically addresses the portion of Idaho south of the Salmon River, and the Code of Federal Regulations provides the detailed Mountain–Pacific boundary. Those are the strongest references when a simplified online map is unclear.
The practical takeaway is straightforward: when coordinating across Idaho, name the city and time zone. It prevents an avoidable one-hour mistake in a state where two neighboring communities can run on different clocks.
Authoritative references
Keep exploring IdahoLens
Published October 12, 2026 · Updated October 20, 2026 · IdahoLens.com