连日来，美国西北部和加拿大西部地区遭遇一股罕见的热浪袭击。多地的温度飙升至40℃以上，打破当地气温历史记录，已有数百人因高温天气死亡。
当地时间6月26日开始，笼罩北美地区多日的“热穹”使得当地气温持续攀升。
美国俄勒冈州、华盛顿州等地最高温度均打破了当地气象观测高温历史纪录，西雅图地区6月30日最高温度接近42.2℃，该州还有地区当日最高气温接近48℃。加拿大不列颠哥伦比亚省更在一周内三次打破全国高温纪录，该省中部的利顿镇6月29日气温一度飙升至49.6℃，防暑形势十分严峻。
不少地区出现电力供应紧张的情况，一些州甚至开始以分区轮流停电的方式，来保障电力供给。
Temperatures in the U.S. Pacific Northwest cities of Portland, Oregon, and Seattle, Washington, reached levels not seen since record-keeping began in the 1940s: 46.1 degrees Celsius in Portland and 42.2 degrees Celsius in Seattle, according to the National Weather Service.
A deadly heatwave continues to pummel Canada's west coast. The city of Lytton in British Colombia has broken the country's all-time hottest temperature three times reaching a record 49.6 degrees Celsius on Tuesday.
由于这些地区纬度偏高，如加拿大破高温纪录的利顿镇，其纬度在北纬50度，已接近我国严寒地区。而西雅图位于北纬47度，属于温带海洋性气候，常年气候较为温和。且一般而言，最高气温记录多发生在七、八月份，这次在六月份就出现打破高温纪录的情况，十分罕见。
世界气象组织发言人努利斯解释说，此次极端高温天气主要是由“大气阻塞模式”引起，这种模式导致两侧的低压形成“热穹”，导致大量热空气凝聚。无法释放的热量向地面压缩，使温度进一步升高。这样持续循环往复，最终形成罕见高温天气。
This week's heatwave was caused by what meteorologists described as a dome of high pressure over the Northwest and worsened by human-caused climate change, which is making such extreme weather events more likely and more intense.
Weather experts say the number of heat waves are only likely to rise in the Pacific Northwest, a region normally known for cool, rainy weather, with a few hot, sunny days mixed in, and where many people don't have air conditioning.
由于这些被“热穹”笼罩的地区此前气候凉爽，极少出现高温天气，不少人很难适应气温骤变，导致此次高温有关的患病人数急剧增多。加上高温容易加速基础疾病的恶化，使得不少身患慢性疾病的老年人纷纷“中招”，成为此轮极端天气的受害者。
据美国有线电视新闻网（CNN）7月1日报道，在美国西北部，华盛顿和俄勒冈州至少有几十人的死亡与此次热浪有关。加拿大不列颠哥伦比亚省在6月25日至30日的5天内至少报告了486起猝死案例，这一数字比往常高出195%，死者多为70岁以上的独居老人。
不列颠哥伦比亚省首席法医官拉庞特称，随着高温天气延续，死亡数字还将进一步增加。
In Canada, British Columbia's chief coroner, Lisa Lapointe, said her office received reports of at least 486 "sudden and unexpected deaths" between Friday and Wednesday afternoon. Normally, she said about 165 people would die in the province over a five-day period.
Many of the dead were found alone, in homes without air conditioning or fans. Some were elderly – one as old as 97. The body of an immigrant farm laborer was found in an Oregon nursery.
In the U.S., Washington state authorities have linked more than 20 deaths to the heat, but authorities said that number was likely to rise.