The heat wave began Monday with most towns across central and eastern Massachusetts topping out between 90 to 92 degrees. This makes 17 days of 90+ in Boston this year, already three more than the average and the most we have had in three years.

Storm conditions could cap off this week's heat wave in Massachusetts, but hot temperatures could make a comeback.

The 39 beaches, including inland ponds and coastal beaches, are primarily closed due to unhealthy bacteria levels or harmful cyanobacteria (blue-green algae) blooms, according to the Massachusetts Department of Public Health’s (DPH) interactive beach water quality dashboard. Only one beach, at Walden Pond in Concord, was closed for “other” reasons.