https://www.boulderweather.com/tags/growing-season/Recent content in Growing Season on BoulderWeather.comHugo -- gohugo.ioenBoulderweather.comSat, 15 Aug 2026 00:00:00 +0000https://www.boulderweather.com/post/boulder-frost-freeze-dates-garden-planning/Sat, 15 Aug 2026 00:00:00 +0000https://www.boulderweather.com/post/boulder-frost-freeze-dates-garden-planning/ <h2 id="what-a-50-percent-frost-date-actually-means">What a &quot;50 Percent&quot; Frost Date Actually Means</h2> <p>Half of the years in Boulder's climate record produced a damaging freeze after May 5. The other half didn't — which is the entire problem with treating &quot;frost date&quot; as a single line on a calendar instead of what it actually is: a probability that shifts week by week through spring and fall.</p> <p>Freeze statistics for a specific place don't come from one average date. They come from a probability table: for a chosen minimum-temperature threshold, what share of the years on record saw a freeze occur on or after a given spring date, or on or before a given fall date. The station-level version of that table for Boulder is served by the <a href="https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?co0848">Western Regional Climate Center</a>, computed from daily temperature readings at the Boulder cooperative weather station across a period of record running from October 1893 to 2016. The <a href="https://www.weather.gov/bou/local_climate">National Weather Service</a> points to this same freeze-probability calculation, and to the parallel version maintained for stations across the state, from its Boulder climate-records page.</p>