New England July Weather Outlook: Back and Forth?

The hottest month of the year has arrived for New England. High temperatures for the region typically peak toward the end of the month before very slowly beginning to slide back down. High temperatures themselves level off this month, only rising a couple degrees from the start to the middle of the month. 

Summary: The overall patterns setting up for July will likely favor back and forth weather with bouts of big heat followed by bouts of cooler weather and back again (which is being seen right now here at the start of the month). Overall the hot bouts may override the cooler bouts and lead to an above average month overall. Near to slightly above average precipitation is favored due to these patterns as well. Read below for the in-depth discussion.

Nantucket's Brant Point Lighthouse. Photo by David Kanigan

TEMPERATURES

New England has started off July with very typical summer weather. This consistent summer pattern will hold true through the first part of July. A large-scale trough is currently in place over northern Canada. A piece of this trough has swung down into New England for the rest of this week. This sent a cold front through New England overnight with another one on the way for Thursday into Thursday night. These fronts will have more of an effect on humidity levels as dew points drop from the mid 60s and 70s down to the 40s to low 50s for the Fourth of July and Saturday.

Heading into the second week of the month (the first full week of July), positive heights and ridging is expected across most of the United States, with ridging most pronounced across the northern tier of the United States as troughing remains over northern Canada. This setup will support near to above average temperatures across most of the United States. 

Below: 500mb height anomaly next week showing riding over much of the US with troughing around northern Canada/Alaska:

Early next week will be the peak of temperatures in the short-term outlook. A ridge axis to the south of New England will create a warm, moist southwest flow. This will likely peak Sunday into Monday (July 6-7), when widespread highs in the mid 80s to mid 90s are likely. This will come with elevated humidity as well. These temperatures early next week will likely propel the week into being above average as a whole, as seen on the Climate Prediction Center’s 6-10 day outlook, which currently covers July 7-11. It’s worth noting that the CPC’s outlook below is rated at a 2 out of 5 for forecast confidence. 

This low confidence level stems from the potential for weak anomalies within the general height forecast (basically, the potential for systems to move through and interrupt the overall ridging). This may come around Tuesday of next week (July 8) in the form of a surface cold front, which could bring unsettled weather and a cool-down from the early week heat. The same basic pattern is occurring this week with heat being tamped down by a frontal boundary on Thursday before building back. The above average warmth being shown mainly stems from the early week heat.

Heading toward the middle of the month, a more pronounced ridge in the west may begin to develop. At the same time, ridging over the central and eastern United States are expected to weaken, with the potential for weak troughing to develop over the central US/Great Lakes by late next week and into the week after. This will push the best chance for consistent hot weather back toward the west, more specifically the northern Plains and Rockies. With that said, ridging may hold on the longest in the east across the northeast, more specifically New England. 

Below: 500mb height anomaly late next week, showing the pattern change mentioned in the above paragraphs:

With all of that said, continued anomalies within the overall pattern being shown are likely. This basically means a continuation of surface features (such as cold fronts) coming through New England, which could potentially mean up and down temperatures (heat builds for a few days before being erased by a cold front and then repeating, similar to what’s being seen right now at the very beginning of the month). 

Heading toward late July, signals may be pointing toward a generally cooler (relative to averages) end to the month. This would come as weak troughing over the center of the country continues to push eastward. A ridge is favored to remain over the west. The main question will be if ridging across the northern United States remains generally in place, or if this is replaced by a full ridge-in-the-west-trough-in-the-east pattern. Only time will tell and smaller-scale factors can’t be predicted this far out, which will play a large role in overall temperatures. 

Overall, we’re predicting generally up and down temperatures with quick bursts of big heat replaced by bouts of near average or slightly cooler bouts of weather and back again. This is how the first part of July is playing out and the long-range signals point to this generally continuing. In the end, we believe the bouts of hot weather will override the cooler bouts and lead to an above average month as a whole. 

PRECIPITATION

With the potential for back and forth temperatures with ridging interrupted by weak troughing or surface fronts, New England may see bouts of dry weather interrupted by unsettled bouts. These may offset and bring New England a near-normal precipitation month overall. There are a couple caveats in July’s precipitation outlook, however. The first is the fact that July precipitation is often convection (thunderstorm) based. This can lead to highly varied rainfall across the region. 

The other caveat is the fact that with hot and humid conditions comes increased moisture in the atmosphere, which can support torrential downpours. A couple systems that bring scattered downpours to New England could thrust the month into being above average. With that said, we’re leaning toward a near-average precipitation month with a better chance to end up above average than below.

LOOKING BACK

June played out pretty much exactly as expected. We predicted a generally mild month overall, with bouts of summer heat and cooler weather. We expected the bouts of summer heat to offset the cooler bouts, which did occur, mainly due to the major heat wave toward the end of the month. We also expected more consistent warmth to develop late in the month as opposed to the beginning, which also occurred. In Boston, the first half of the month saw seven below average days and seven near or above average days. The second half saw four below average days with eleven near or above average days. 

Precipitation played out a bit differently than we were thinking, however. While we did state New England has a lower chance of above average precipitation, we did note that there were “reasons to believe” New England would end up above average. The main reason was the potential for “scattered downpour” days, similar to what we’re saying for this month. That didn’t really pan out and much of New England saw a rather dry June.