First frost date

The first frost date is the median date in fall when freezing temperatures first arrive (NOAA 1991–2020 normals, 50% probability). Fall gardens count backward from it: garlic goes in about 6 weeks before, fall lettuce 7 weeks before. Like the last frost date, it is a coin-flip median — a 10% probability date sits later and marks the realistic deadline for harvests.

See also: Last frost date · Fall garden