Many Washingtonians are tiring of the rain, but, unfortunately, just as May was a humid and wet month, our analysis of available models and trends have us leaning toward expecting a wetter than normal June
On the plus side, our wet May has steered us clear of any serious drought concerns, and all the moisture will tend to keep temperatures from sweltering, at least at the beginning. Overall, we think temperatures will end up pretty close to normal in meteorological summer’s first month.
Historically, the month ranks as our third hottest (after July and August) and second wettest (after May). We think this June will live up to its earned sticky and soggy reputation.
Average temperature: 74 to 76 degrees, which is right around the normal of 75 degrees. This is similar to 2016 and cooler than last year.
Rain: 3.5 to 5 inches, compared with the normal of 3.78 inches, which would make it the wettest since 2015.
The thinking behind our outlook
Since 2000, June temperatures in Washington have been above normal two-thirds of the time, while it has been wetter than normal about half of the time. This year we have an interesting situation as models project lower-than-normal temperatures in the month’s first week, with comfortable 70s for highs. Beyond that, modeling suggests that the main heat in the country flutters back and forth between the Western and Central United States instead of here in the East. However, muggy conditions could still keep our low temperatures warm enough to edge our average June temperature slightly above normal, anyway, especially with all of the soil moisture courtesy of our soggy May.
The charts on the left rank June temperature and precipitation since 2000. Last June was included in the “Super Hot June” groupings as it was one of the hottest of the 2000s with even a period of roasting middle-90s at mid-month. This year may be closer to 2016 or slightly cooler, given our cooler start to the month.
In terms of rain, the wettest of all-time and of the 2000s was 2006, while last summer was bone-dry and driest of the 2000s. Our call for a wetter-than-normal month is slightly easier than the temperature forecast, because we are expecting heavy rain over the month’s first several days to give us a head start in reaching our normal of 3.78 inches.
Developing El Niño. The slow trend toward El Niño can have a cool and wet influence on the summer forecast, but the influence is typically not as strong in June. Exceptions include the faster-developing El Niños in 2009 and 2004, which likely did exert a cooling effect on June temperatures. This year’s El Niño development is probably more like 2006 (which had near normal temperatures) or 2002 (slightly above normal), which evolved more slowly.
Warmer waters in Northern and Eastern Pacific. These areas are warmer than last year and tend to correlate with big heat domes over the U.S. remaining west of our area. The West and sometimes the mid-continent have better chances for more consistent heat than we do on the Eastern Seaboard, given this ocean temperature configuration.
Model guidance. The 15-day medium range models favor a cool week next week and then closer-to-normal temperatures during the second week of June. Then both the European and CFS weekly outlooks favor near-normal temperatures more often than not for East Coast cities for the second half of the month. The CFS model forecasts for the month of June are shown below, and they lean wet with near-normal temperatures.