Hillsboro, OR 97123 Frost Dates
Hillsboro, OR: when does the frost end?
Typically, the last spring freeze lands around 02/11, roughly 167 days out. Fall's first freeze usually shows up around 12/05, roughly 303 days after the last spring frost.
Zone 8b (15 to 20°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Hillsboro, not a forecast for this year.
Stretching the season past the first frost
With roughly 14 weeks until Hillsboro's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Hillsboro's last frost
02/11 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/05 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/26 and only about 1 year in 10 sees frost after that.
Hillsboro against the rest of the dataset
At roughly 303 frost-free days, Hillsboro places 3,767 of 40,283 ZIP codes in this dataset. Within OR, it ranks 14 of 463.
Learn more
Before leaning on 97123's figures: the frost range explains how to read the range around Hillsboro's dates instead of trusting one, while local microclimates explains what one yard in Hillsboro can differ from the 97123 normal.