Average Frost Dates

Our first frosts are approaching! Soon we’ll be crunch crunching through the grass and scraping off our windshields in the morning.

The average first frost date is just that – an average – so it’s a good idea to familiarize yourself with the norms for your area and plan accordingly. Frosts can occur much earlier or later than typical.

There are a number of factors that contribute to frost and temperatures can vary by neighborhood or even block to block. For instance the average first frost in downtown Portland is typically three weeks after the first frost at the Portland Airport. In outlying areas like Canby and Forest Grove the average first frost is usually in mid-October.

Average Frost Dates

Statistics used to formulate first and last frost dates are drawn from weather data collected from 1981-2010. All data is collected at low elevations. Chart source info is from the Oregon Climate Service at OSU.

Before frosts arrive, tend to a few tasks:

• Bring houseplants and frost-tender plants inside. Examine plants closely, looking for slugs and pesty insects and insect eggs. Remove, wash off, or apply insecticides if needed.
• Harvest the last of your warm-season fruits and veggies. Tomatoes, summer squash, eggplant, peppers, cucumbers, potatoes, fall raspberries and ripe apples and pears should be harvested. Install season-extenders in your vegetable garden. Cloches, row cover, and cold frames can all be used to protect fall veggies from frost or heavy rain and elevate temperature. Read more here in the downloadable booklet: Fall and Winter Vegetable Gardening in the Pacific Northwest put together by Oregon State University, University of Idaho and Washington State University.
• Sow cover crops.
• Plant spring bulbs! Many bulbs like tulips and daffodils can be planted after frosts, but should be in the ground before soil is saturated or frozen. October is the perfect month.
• Protect geraniums and tender fuchsias. Prune branches down to about 6”, remove thin wispy branches entirely, check for and remove slugs or aphids and store in a cool (not below 40f) dark space for winter. Here’s a helpful walkthrough from the Oregon Fuchsia Society.