Meteorological summer begins Saturday, but our weather in the first month of the new season won’t stray much from the overall warm and wet pattern that has persisted for months.
Although we’ll see cooler temperatures and a brief taste of springlike weather early next week, we favor slightly above normal temperatures overall and wetter than normal conditions in June.
It should follow the tendency of May, which will end up warmer and wetter than normal, and most months since last summer.
For perspective, normal June rain is 3.78 inches, and the normal average temperature is 75.2 degrees. Our forecast confidence is moderately high on rainfall, but moderately low for temperatures.
The main weather pattern driver is El Niño, the large area of warmer than normal waters over the east and central tropical Pacific Ocean. Although it’s a relatively weak El Niño, the atmospheric response has been strong, with an active and stormy U.S. jet stream pattern and lots of associated rain.
When tropical waters are very warm, it strengthens the temperature contrast between the high and low latitudes. This, in turn, revs up upper-level winds, establishing an active, stormy jet stream pattern.
The intensity of the global wind is the highest since 2009, and computer models suggest it may increase in early June. Faster global wind speeds tend to mean cooler temperatures, too, which we’ll experience early next week. However, in recent years, the associated increase in storminess, cloud cover and humidity has raised nighttime temperatures.
Wet and warm have generally gone hand-in-hand over the past decade. Here is the list of wettest 10 Junes since 2000 in Washington:
Three of the wettest Junes have occurred since 2010, and all three of those years, as shown below, were also warmer than normal.
The latest projections from NOAA’s CFS model support the outlook for a marginally warm and wet June, helping to boost our confidence to some degree.
Forecast temperature difference from normal
Forecast precipitation difference from normal
Nationally, the model is forecasting near-normal June temperatures, something the United States hasn’t observed since 2009. A cooler-than-normal June hasn’t occurred since 2004, 15 years ago. So, even though a strong signal isn’t present in computer models, recent history favors leaning warmer.