Today’s weather marks a notable change as a thick marine layer has settled over the region west of the Cascades, unlike the consistent warm and hot weather experienced in recent summers. This marine layer phenomenon was more common in the past but has become a rarity in today’s warming climate.
Portland reached a high of only 71 degrees today, making it the coolest day in over two months. Just two weeks ago, the low temperature was warmer than today’s high. This marks the end of the fifth and likely final heatwave of 2023, with temperatures reaching 94 degrees for three consecutive days. This heatwave was ended by the arrival of marine air pushing inland.
Despite the change in weather, August 2023 is still on track to be the warmest August on record in Portland, with an average high temperature of 76.1 degrees. It was predicted in the past that as summers warmed, Portland would experience temperatures similar to that of Roseburg or Medford in the 1990s. This prediction has held true, as the average high temperature this month has been in the upper 80s.
Other stations in the region are not experiencing temperatures as high as Portland, indicating the increasing prominence of Portland’s nighttime urban heat island effect. Nonetheless, it has been another scorching summer month for those living further inland from the coastline.
Looking ahead, the weather models for the next 10 days show a lack of heat, indicating the transition into September-like weather. The forecast indicates upper-level troughing along the West Coast, making hot temperatures in the 80s and 90s unlikely. Showers are expected intermittently during this period, with Thursday potentially being a rainy day. This rainfall, combined with cool temperatures and higher humidity, will help alleviate the fires in the area.
The forecast for the next two weeks also predicts multiple chances of showers, particularly in the first seven days. The temperatures are expected to be pleasant, providing relief from the previous hot weather.
In summary, while the stream of hot and sunny days has come to an end for the season, warm weather will still persist in the next 10 days. Showers will occur but heavy rain is not expected at this time. It is important to note that this is not the beginning of the fall rains, which typically occur later in September. Those tired of the hot weather can enjoy the upcoming 7-10 days of milder temperatures.
As a practical effect, the changing weather has resulted in a decrease in water temperature. For example, above-ground pools that had reached temperatures of 89 degrees during the heatwave are now around 80 degrees. With the low sun angle and longer nights approaching, the water will not warm up as much, even on a 90-degree day. This indicates the gradual fading of summer in the next two weeks.