I-5: The Pacific Coast Spine

Interstate 5 is the only continuous freeway connecting Mexico and Canada through the United States, running 1,381 miles from San Ysidro at the California-Mexico border to Blaine, Washington at the Peace Arch crossing into British Columbia. It is the dominant freight corridor of the West Coast, moving produce out of the San Joaquin Valley, container traffic between the ports of Long Beach, Oakland, and Tacoma, and timber and agricultural products from the Pacific Northwest.

The route splits cleanly into three personalities. From San Diego through Los Angeles and up the western edge of the San Joaquin Valley, I-5 is largely a flat agricultural expressway crossed by the Tejon Pass (Grapevine) at 4,144 ft, a 6% grade that closes for snow several days each winter. Through Northern California it climbs into the Cascades over Siskiyou Summit (4,310 ft), the toughest sustained climb on the entire interstate, before descending into the Rogue Valley of Oregon. From Eugene north through Portland, Olympia, Seattle, and the Skagit Valley, I-5 becomes a dense urban interstate routinely choked with congestion in the four-hour Portland-Seattle-Tacoma chain.

For commercial operators, I-5 carries most of the West Coast's long-haul freight. CHP and Oregon DOT enforce truck-specific speed limits and bridge weight restrictions aggressively, and the Siskiyou-Shasta corridor has a string of staffed weigh and inspection stations on both the California and Oregon sides of the summit. Chain controls are routine November through April from the Grapevine north.

• Only US interstate that touches both the Mexican and Canadian borders
• Crosses Siskiyou Summit (4,310 ft) on the California-Oregon line, the highest point on the entire I-5 route (Wikipedia: Interstate 5)
• Tejon Pass / Grapevine (4,144 ft) closes 5-15 times per winter for snow
• Carries the bulk of Port of Long Beach and Port of Tacoma container drayage
• Routes through downtown Sacramento via the I-5 / Capital City Freeway interchange
• Designated CARB-compliant corridor in California. Pre-2010 trucks face restrictions.
• Concurrent with no other interstate for any significant distance, runs solo end-to-end

The passes on Interstate 5 with a full guide: grade, chain-control season, closures and hazards. The status is the state DOT's latest reading.

• Tejon Pass (Grapevine), California, 4,144 ft: Open
• Siskiyou Summit, Oregon, 4,310 ft: No current report

Chain rules for the states these passes are in, and for every state on the route that has a chain law:

• California chain law
• Oregon chain law
• Washington chain law

National Weather Service alerts in force in the states Interstate 5 runs through. Each one covers a county or a forecast zone, which may be far from the Interstate.

• 2 alerts in California: Coastal Flood Advisory, Wind Advisory
• 2 alerts in Washington: Frost Advisory, Wind Advisory