Water boils at lower temperatures as altitude increases. At sea level, water boils at 212°F (100°C). At 5,000 feet, it boils at approximately 203°F (95°C), and at 10,000 feet, only about 194°F (90°C). Since boiling water canning relies on heat to destroy harmful microorganisms like Clostridium botulinum (which causes botulism), lower boiling temperatures mean less effective sterilization. Additional processing time compensates for this reduced heat penetration, ensuring food safety.

You can find your elevation several ways:

• GPS/Phone: Most smartphones display elevation in their compass or maps app. Our "Detect My Altitude" button uses your device's GPS when available.
• Online Tools: Websites like whatismyelevation.com let you enter your address.
• USGS Topographic Maps: Free at usgs.gov for U.S. locations.
• Local Extension Office: Your county's agricultural extension office can provide accurate local elevation data.

Dial Gauge: Has a precision dial showing exact pressure. Allows fine adjustments (e.g., 11, 12, 13 lbs). Requires annual calibration checks for accuracy. At higher altitudes, pressure is increased in 1-lb increments at specific elevation thresholds.

Weighted Gauge: Uses a metal weight (often a "jiggler" or "rocker") that sits on the vent pipe. Simpler and doesn't need calibration. Typically comes with 10-lb and 15-lb weights. At elevations above 1,000 feet, you simply switch to the 15-lb weight.

Above 10,000 feet, water boils at approximately 194°F (90°C) or lower, which is insufficient to reliably destroy botulism spores even with extended processing times. The USDA and National Center for Home Food Preservation strongly recommend using a pressure canner for all foods at elevations above 10,000 feet. If you must water-bath can, add 1 minute per additional 1,000 feet beyond the standard adjustments, but this is not a validated safety recommendation. Pressure canning is the only method proven safe at extreme altitudes.

For pressure canning, the processing time generally stays the same as your recipe indicates (usually based on sea-level standards). Instead of adjusting time, you adjust the pressure upward to compensate for altitude. This is because pressure canners create an artificial environment where the internal temperature can reach 240–250°F regardless of external air pressure — as long as the gauge pressure is correctly set for your elevation. Always follow your recipe's processing time; only change the target pressure based on altitude.

For water bath canning, the altitude adjustment (added minutes) is the same regardless of food type — whether you're canning jams, pickles, fruits, or tomatoes. The adjustment compensates for the lower boiling point and applies uniformly. However, always start with the correct base processing time for your specific recipe and jar size, then add the altitude adjustment. For pressure canning, the pressure adjustment is also food-independent; only the base pressure recommendation varies by food type (typically 10 or 11 lbs at sea level for most foods).

Below sea level (e.g., Death Valley, CA at -282 ft / -86 m, or areas near the Dead Sea at -1,400 ft / -427 m), water actually boils at a slightly higher temperature than 212°F. However, the standard canning times and pressures designed for sea level are still fully adequate and safe. No downward adjustment is needed. Simply use the sea-level standard times and pressures. The recipes' built-in safety margins already account for minor variations.