Spokane passed the average date of its last freeze yesterday, which was May 4. Considering we just emerged from the city’s seventh coldest April in recorded history, it’s hard to imagine planting a garden anytime soon.
As we’ve seen in the past, the average date of the season’s last freeze is no guarantee that it’s safe to plant. The date fluctuates and is also highly variable across different locations in the Inland Northwest. On average, the Lewis-Clark Valley has its last freeze on April 15, according to data compiled by the National Weather Service. In Spokane, it’s the first week in May and in Pullman it’s the second week. Meanwhile, Sandpoint’s last-freeze date is May 18.
Even in Spokane proper, the date can vary slightly due to the city center running slightly warmer than the areas surrounding it.
The last time we saw a freeze in the Lilac City – when the temperature dips to 32 degrees or less – was on April 22 when the overnight low dropped 32 degrees. Since then, we’ve had a few close calls, including 33 degrees on April 27 and 34 on April 28.
May started off cool as well, with below normal temperatures on Sunday and Monday of this week. The coldest time periods tend to occur between 4 to 5 a.m. this time of year, which means plants are typically most vulnerable just before sunrise.
In 2021, the season’s last freeze in Spokane occurred on April 12. In Pullman, it was nearly a month later on May 9. Coeur d’Alene dipped to 31 degrees on April 22. Ironically, that month was the seventh warmest April, compared to the seventh coldest April this year. Looking at previous years, two very late freezes in the Spokane area occurred on May 21, 2004 – when a half-inch of snow fell – and again on May 25, 1964, when the mercury dropped to 31 degrees. The coldest temperature recorded was 24 degrees on May 8, 2002, frigid enough to turn the leaf tissue of young marigold and tomato plants into mush.
As we close the book on one of our cooler Aprils, the chilliness may linger through this month, according to the May outlook issued by the National Weather Service Climate Prediction Center. Odds favor the final month of spring to have cooler than normal temperatures with damp conditions across Washington state, the Inland Northwest included.
Obviously, just because the calendar says it’s time to plant doesn’t mean weather conditions will abide. That said, we’ll defer to the wisdom of the Spokane County Master Gardeners. As the group says on its website: “Planting a little late is the best method.”
Nic Loyd is a meteorologist in Washington state. Linda Weiford is a writer in Moscow, Idaho, who’s also a weather geek. Contact: firstname.lastname@example.org.
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