As September ends, the weather patterns in New England are undergoing a transition from a summer-like pattern, in which forecasts are dominated by sunshine and sea breezes punctuated by occasional showers, to a more fall-like pattern, in which temperatures and precipitation begin to fluctuate more wildly with the comings and goings of frontal systems. October also signals a general cool-down: While temperatures in Boston reached 87°F (31°C) this past Sunday, normal high temperatures will dip down to the mid-50s °F by the end of the month.
The transition to cooler temperatures begins now, with highs not expected to exceed 70°F for the rest of the week. Sea surface temperatures off the coast of New England remain relatively moderate at this time of year, so onshore flow will keep temperatures in Cambridge at or around 60°F (16°C). A low pressure system off the coast will keep the chance of rain in the forecast for today and tomorrow. A brief warm-up is expected on Friday before the next storm moves through on the weekend.