The U.S. Department of Agriculture (USDA) released a revised version of its Plant Hardiness Zone Map, the first such update since 2012.

The backsides of seed packets will never be the same. Gardeners, landscapers and others refer to the zones on seed packets to decide whether or not a plant is likely to thrive in their geographic area.

The 2023 version of the map shows about 50% of zones shifting to the next warmer one. This indicates that these areas warmed up somewhere between 0 to 5 degrees Fahrenheit over the past 11 years.

According to the USDA press release that announced the news, the new map is more accurate and contains greater detail than prior versions. The 2023 map incorporates data from 13,412 weather stations compared to the 7,983 that were used for the 2012 map.

The hardiness zones are based on the average annual extreme minimum temperatures over the past 30 years. The annual extreme minimum temperature represents the coldest night of the year, which can be highly variable from year to year, depending on local weather patterns. The USDA noted in their announceent that the zones do not suggest these are the lowest temperatures ever recorded in these areas, nor the coldest temperatures that might occur in the future.

Here’s the Zones for the Four Largest Texas Cities and their lowest temperatures

  • CHANGED Dallas–Zone 8b, 15-20 degrees (from 8a)
  • CHANGED Houston–Zone 9b, 25–30 degrees (from 9a)
  • NO CHANGE San Antonio–9a, 20 – 25 degrees
  • CHANGED Austin–9a, 20-25 degrees (from 8b)

Thirteen hardiness zones comprise the map across the United States and its territories, with each zone broken into half zones, designated with an “a” or “b” following the zone number. For example, Zone 5 is divided into 5a and 5b half zones.

Want to check your hardiness zone? Check out the map and put in your zip code here. 

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