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Wyoming: Risks & Trends

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Same standard as every other page on this site: every figure below is independently sourced, and figures that vary across sources, or measure genuinely different things, are flagged as such rather than collapsed into one number that looks more precise than the underlying data actually supports.

The Yellowstone Caldera

MetricFigure
Annual probability of a caldera-forming eruption ~1 in 730,000 (~0.00014%)
Comparable risk Roughly similar to the odds of a large (1 km) asteroid striking Earth
Current magma chamber state 5-15% molten material, not a solid pool of ready-to-erupt lava
Current USGS assessment No indication that a major eruption is approaching
Regional impact if it occurred Pyroclastic flows affecting the nearest parts of WY, MT, and ID; falling ash affecting a much broader area of the country

Why this is worth a page at all, given the odds

A 1-in-730,000 annual probability is genuinely negligible for day-to-day planning purposes, and nothing here should be read as suggesting otherwise. It’s included because the site’s standard is to name every hazard with real regional-to-national consequence potential, however unlikely, and to give readers the actual numbers rather than either alarmist framing or silence.

The Blizzard of 1949

MetricFigure
Start date January 2, 1949
Peak winds 65-80 mph
Cheyenne snowfall, initial surge 20-30 in within days
Total event duration ~2 months of repeated snow and bitter cold following the initial storm
Deaths 12 (Wyoming)
Rescue effort 10+ state and federal agencies involved, including the U.S. Army and National Park Service
Historical ranking Widely considered the worst winter storm in Wyoming's recorded history

A storm, then a season, not a single event

The Blizzard of 1949’s initial multi-day storm was followed by roughly two more months of repeated snow and extreme cold across Wyoming. Its reputation as the state’s worst storm reflects that extended pattern, not just the opening blizzard’s snowfall total.

Sources