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Dangerous Heat Wave Underway

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HARDWICK – A healthy balance of sunshine and light precipitation was the theme of last week’s weather. The second half of the work week featured mild temperatures, some scattered showers, and periods of broken cloud cover. Although early last week it was predicted that a ridge would be building in over the region, it did not evolve as quickly as previously expected. Thus, temperatures over the weekend were lower than normal with highs in the low- to mid-70s, with lows falling into the 40s. Around a tenth of an inch of rain was reported at local rain gauges.

photo by Vanessa Fournier
Sunshine brightens a cool Saturday afternoon on Route 2 in Marshfield, June 15.

That ridge is now starting to strengthen, with rapidly rising temperatures leading to several days of highs expected to exceed 90 degrees. Even on Monday, the humidity was starting to rise and make the apparent temperatures feel like they were in the 80s. We expected highs on Tuesday to reach 90°, with heat index values in the mid- to upper-90s. Today’s projections show heat index values in the low-100s, with temperatures reaching the mid-90s. One more day of hot weather is expected tomorrow, before a frontal system sagging south from Canada removes some of the heat and humidity for Friday.

In the meantime, it’s important to understand how heat and humidity can impair the body’s ability to regulate temperature. We have several ways that our body allows us to lose heat, including evaporation and convection. Evaporation is the process of accelerating heat loss through moisture leaving the surface of the body and turning into a gas. Convection is the process of air moving over a surface that removes heat as it passes over the surface. In conditions this extreme, these mechanisms for losing heat do not work as well, as the increased humidity inhibits evaporation, and the warm temperatures limit the gradient needed in convection. Why does that matter? Limiting exercise and exposure to the outdoors will reduce your risk of developing heat related illnesses. It is also important to stay hydrated and seek out air conditioning during the most extreme conditions. The National Weather Service has issued a heat advisory, which lasts until 8:00 PM on Thursday.

Thursday evening, with the approach of the frontal system, we may see some scattered severe thunderstorms and very heavy downpours which will last into the day on Friday. We see a brief cool-down for Saturday. Another frontal system approaches on Sunday bringing warm and humid air back into the region, although not as intense. Strong showers and thunderstorms are likely to develop as we approach the evening hours on Sunday. The passage of this frontal system will allow us to return to some seasonably normal temperatures as we start next week. Here are the details of the forecast:

Wednesday: Mostly sunny. Isolated showers and thunderstorms in the afternoon. Hot. Hi: 94. Low: 71. Heat index values as high as 103.

Thursday: Mostly sunny. Scattered showers and thunderstorms developing in the afternoon. Some thunderstorms may produce damaging winds and heavy rainfall. Hot. High: 91. Low: 67. Heat index values as high as 99.

Friday: Mostly cloudy with some clearing in the afternoon. Scattered showers and thunderstorms. Hi: 82. Low: 63.

Saturday: Mostly cloudy. Scattered showers. High: 73. Low: 61.

Sunday: Increasing clouds. Numerous showers and thunderstorms developing by evening. Some of those thunderstorms may be strong. High: 81. Low: 66.

Tyler is our weather reporter and a community journalist. He works as a nurse and EMT, volunteers with Hardwick Rescue and helps to train new EMTs.

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