Can you plant your seeds yet?

 This time of the year, I start thinking about my vegetable garden and whether the soil is warm enough to plant some seeds.

Certainly, the weeds have started to sprout and grow.

So let's check with our friends at the AgWeatherNet at Washington State University.

Below is the latest soil temperature at 2 inches down.  Lower to mid-50s in western Washington and 50s to lower 60s in eastern Washington.    The warmest soil is around Yakima, which is typical.

I sometimes muse about why the Yakima area is so warm.  Yakima is in the sinking zone southeast of the Cascades, with the sinking air warming by compression and reducing any clouds.   Fewer clouds means more warming solar radiation.  You can see the effect today at noon (see visible image below).

The SNAP satellite can measure soil temperature from space....here is a view of the entire West Coast three days ago.  Nice and warm soils in California and southern Nevada, with the Yakima to Tri-Cities area the warmest in the NW.

Consider the plot of 2-inch soil temperature at Seattle (near the Urban Horticulture Center at the UW).  Soil temperatures had dropped into the 30s back in February during our extended cold period, but it is now just about 50°F.  It was around 60°F in mid-October.

Now, back to the big question: what seeds can we plant now? 

 Considering the following table, there are plenty of vegetable seeds that can be started now, particularly the leafy veggies.  But not beans, squash, and melons, which require warm soil.  

Time to get working!

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Announcement

I will hold a special online Zoom session at 8  PM on Sunday for Patreon supporters. I will talk about the latest spring/summer forecasts and answer your questions.

April 1 Special: The Initiation of UW ClimateLab Reports

 Concluding that if you can't beat them, join them, today I will start the first in a series of UW ClimateLab examinations on the effects of global warming on our region.

In this issue, let's examine the effects of global warming on spring (March-May) conditions in the Northwest by looking at trends from 1950-2024.

In western Washington, Olympia Airport is a good place to start, since there is less urbanization than central Puget Sound (see satellite image for the surroundings, below)

Starting with the annual highest spring temperatures (below), there is nearly no long-term trend (brown line).   Very surprising......and disappointing for those who enjoy warmth in spring.

In contrast, there is modest warming for the average springtime high--by about 2°F since 1950.

The mean minimum temperature has warmed up by about the same amount (2°F)

Precipitation at Olympia? Up about an inch.

ClimateLab conclusions:  No increase in extreme highs.  A little moister.  A Modest 2F increase in average highs and lows.

Now let's turn to Eastern Washington...and you can't go wrong with Ephrata, which is hardly in an urban neighborhood.

For the highest spring temperature, there has been no upward trend.  Nada.

The mean daily high temperature has increased slowly, by about 2.5°F since 1950

And surprisingly, the mean minimum temperature has cooled.

Spring precipitation has increased slightly.

Bottom line:  very similar to Olympia, with precipitation increasing slightly, the extreme temperatures remaining the same, and the average high going up about 2°F.

Virtually all stations in Washington State without urbanization or other issues are similar.  

Extreme springtime highs are not going anywhere, and precipitation is modest.  Average highs have gone up about 2°F in 75 years, without acceleration of the warming.

The ClimateLab will allow you to decide whether this is an existential threat or a crisis.

Happy April 1.

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Important Notice:  My UW talk will be delayed until April 17.