35th Anniversary logo for Friends of Casco Bay

Warming Waters Are Hot Topic

As the purple line for 2020 shows, temperatures measured at our Continuous Monitoring Station in Yarmouth, Maine, are setting records. Our staff, board, and volunteers are using data from the station in conversations with community members and decision makers to explore what we need to do to address and adapt to changes that are happening.


Day after day, we watched temperature records being set. This year has been hotter than usual. Out of the first 243 days of this year, January through August, 2020,  132 days exhibited a daily average temperature higher than established for that day in any of the prior four years, 2016 – 2019.

“While warm water temperatures may have been great for swimming in the Bay,” says Staff Scientist Mike Doan, “there are significant downsides to warming water. Less oxygen, more invasive species, changes in the ocean food web, and the growth of nuisance and harmful algal blooms are all associated with warming temperatures.”

In addition to hourly data collected at the station, Friends of Casco Bay’s staff monitor another 22 sites around the Bay as part of our seasonal spot-checks. Those sites, too, have been extremely warm. Our offshore site in Broad Sound saw temperatures near 22°C [almost 72°F], and the upper New Meadows River had temperatures over 25°C [nearly 80°F].

Other researchers have noted similarly high temperatures offshore in the Gulf of Maine this year. In August, NOAA satellites measured an average sea surface temperature of 68.93°F, nearly reaching the record set in 2012.

These data are critical as we continue our advocacy work with the Maine Climate Council at the state level and Portland and South Portland’s One Climate Future initiative at the local level, to address and mitigate the impacts of looming changes.

“What we have been seeing this year reaffirms for me the urgency of our collective work to document change, address the root causes of climate change, and prepare for its consequences at community, regional, state, and national levels,” says Casco Baykeeper Ivy Frignoca.