The first week of meteorological summer continued the hot theme seen in the western U.S. so far in 2016, sending the mercury soaring and records falling.

The jet stream surged northward over the West last weekend, sending record heat from the Southwest to the Pacific Northwest. That bulge in the jet continues to migrate eastward across the country, which will send temperatures 10°-15°F above normal from the Dakotas to the Great Lakes this weekend. This means highs in the 90s in the Dakotas and upper 80s in parts of the Great Lakes states.

May temperature anomalies across the U.S.

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Several spots in the West set new high temperature records last week. Phoenix is normally hot this time of year, with a normal high of 102°F (39°C), but there were four consecutive days (June 3-6) when the high was more than 110°F (43°C). Each of those four days brought a new record high, with the temperature peaking at 115°F (46°C) on June 4.

Even traditionally cooler spots of the Pacific Northwest have been especially hot. According to the National Weather Service in Seattle, the average temperature for the first week in June this year has been the second hottest since the 1890s. Similarly, the high of 84°F (29°C) on June 7 marked the 14th day that was 80°F (26.7°C) or warmer this year. The record for the most days at or above 80°F by the end of June is 15, which was set just last year.

Portland, Ore., is typically a bit warmer than Seattle, and record highs were set both Saturday (97°F, or 36°C) and Sunday (100°F, or 37.8°C). These records were smashed, as the Saturday record was exceeded by 6°F (3.3°C), and the Sunday record by 4°F (2°C). Sunday’s high marked the second earliest date that Portland had reached 100°F. The only earlier time was May 28, 1983.

During the three-day period from June 4-6, 175 new record high temperatures were set in the western U.S. Bullhead City, Ariz., hit 121°F (49.4°C) on June 4, breaking its old record high by 3°F (1.7°C). Two days later, Lemon Cove, Calif., reached 107°F, (41.7°C) which eclipsed its old record by 1°F (0.5°C), especially notable as the records there go back 117 years.

The heatwave has ended in the Pacific Northwest for now, but according to the Southeast Regional Climate Center, both Seattle and Portland are having their hottest year on record so far. While several areas east of the Continental Divide have seen the heat ease back in the last several weeks, the West continues to bake.

Temperature data released by NOAA on Wednesday bears this out. Nationally, May was near normal, but Oregon and Washington each had one of their 20 warmest Mays on record. Year-to-date, the country is having its fifth warmest year on record, and the West is leading the way. Washington, Oregon, Idaho and California are each having their fourth warmest year so far.

 

The increase in extreme heat is one of the hallmarks of climate change. As the amount of greenhouse gases in the atmosphere continues to grow from human activity, the incidents of what we consider to be extreme heat today will become more common in the coming decades.

If the current rate of emissions continues, both Seattle and Portland should expect to have a dramatic rise in the number of days each year over 90°F (32°C). Locations like these will have to be ready for a more consistent level of heat than experienced in the past. The people living there will need to prepare for such changes, including a shift in planting zones and possible new insects migrating into the area from previously warmer climates.