Massachusetts summer outlook: What seasonal forecasters expect in greater Boston

Weather across Massachusetts and New England always feels like riding a roller-coaster, but some patterns and trends define what type of conditions will be typical for the season to come. Harvey Leonard, chief meteorologist emeritus, received insight from three forecasting experts to get a picture of what may be to come. "I think this summer's going to be a warm one," Dan Leonard, a long-term weather forecaster at Andover-based The Weather Company said. Leonard (no relation) thinks this summer may end up as much as one to two degrees above normal. By contrast, Boston was 0.8 degrees below normal during the rain-soaked summer last year, and 2.2 degrees above normal during the rain-starved summer scorcher of 2022.But, a lot will ride on how the next few weeks play out."It's all going to depend on how much rain we get, heading into the summer," Leonard said. "If we do get a lot of rain, continuing this rainy season that we've had late winter and early spring, then it's going to be really hard to get a very hot summer. In fact, it's more likely to be very humid."That humidity, beyond making it more uncomfortable, plays another key role in how warm our summers have been and likely will continue to be. "Most of the warmth that we're seeing is because of higher overnight low temperatures rather than higher daytime temperatures," Leonard said. A RAPID SHIFT OR A SLOW SLOG INTO SUMMER?“I don't think we're going to start off hot (or) really (be) off to the races on the temperature,” Dr. Judah Cohen, seasonal weather forecaster with Lexington-based AER/Verisk said.Cohen thinks that true summer heat may not arrive until closer to July 4th, leading to a slow lead-up to summer ahead for New England.But perhaps the biggest question you might have is: How often will your plans get rained out like so many were last year? Summer rains have been sort of a ‘feast or famine’ lately.“I don't think we'll have something like two summers ago where we had that drought and I don't think we'll have as wet a summer as we had last year,” Cohen said. He is forecasting a summer with normal to slightly above-normal rainfall. Forecasters are pointing to a pattern that should emerge, starting in the Pacific Ocean. Very warm ocean waters in the central Pacific will send the jetstream northward. But, the water off the West Coast is actually relatively cool and a trough will likely set up in that area, making the West Coast a little cooler. This ridge trough pattern will repeat over the central plain, where searing heat will be found for much of the summer. This all could leave the Northeast and a kind of transition zone, leaving this area swaying between a summer sizzler and mild and mellow.What may not be so mellow, is the chance for some serious storms over the Atlantic.“The big wild card, of course, is what's going to happen with the tropics and whether a storm is going to make its way up into our neighborhood,” Dr. Jennifer Francis, a senior scientist with Falmouth-based Woodwell Climate Research Center said.The strong El Niño pattern has changed to a La Niña. That typically favors more activity in the tropics.“That, in combination with the raging (warm) ocean temperatures all throughout the tropical Atlantic and right into the Caribbean and the Gulf of Mexico, those two factors combined are leading most tropical storm forecasting centers to predict an incredibly active season,” Francis said.And it only takes one landfalling tropical storm or hurricane to make a season active. “Just the fact that there are more of them gives us better chances of having one come ashore somewhere. Everybody everywhere from the Caribbean all the way up to Nova Scotia should be on high alert,” Francis said.The pattern we should be in for most of the summer might help steer storms out to the ocean before they reach Massachusetts and New England.