THE PRESSURE IS on when you decide to fly a trip with known low IMC weather at your destination. What is "low IMC," more commonly called "low IFR"? It's when the ceiling is at or below 500 feet and the visibility at or below one mile. Yes, visibility is the governing variable, because even though a ceiling may be uncomfortably low you may still be able to see the runway environment through cloud bases well enough to land. But that's a technicality. If the weather is that bad, you'd better be on your toes. So, how low can you go on a Category I instrument approach in low IFR conditions? The first place to check is the airport's instrument approach plate. The lowest permitted altitude and visibility will be published at the bottom of the page. These will vary from airport to airport, depending on the type of the approach, nearby terrain, obstacles, and lighting systems. It's also important to check the notes at the top of the page. There may be situations where your approach minimums may be different than those published-an airport without weather reporting on site will have higher minimums, for example. Or a note may say that the approach is not authorized (NA) at night.
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