Before we get to the weekend heat let me just say that the amount of rain around greater Boston yesterday was paltry and did almost nothing to alleviate our dry weather. Today will be a real beauty with lots of sunshine and temperatures getting well into the 70s. It will be cooler at the coast, with parts of Cape Cod likely remaining in the 60s this afternoon.
As the heat arrives overnight, there will be a line of clouds and perhaps even a few showers. There is even a possibility of a downpour as the warm weather surges north. If this did occur, any showers would end early Saturday followed by quick clearing. The best chance for this would be overnight and south of the Mass. Pike.
Although the actual temperature Saturday afternoon will likely climb slightly above 90 degrees, it will take us a little while to get there. This means that the first few hours of the day will be quite comfortable, running from the 60s to the 70s to the 80s and it will take until early afternoon before the heat is really here. This time of the year high temperatures are often reached between 4:00 and 5:00 p.m.
Humidity will also rise during the day Saturday and continue to increase into Sunday. This will keep temperatures Saturday night from falling below 70 degrees in many areas. When you wake up Sunday, it will feel quite sticky. Temperatures will reach 90 degrees several hours earlier than the day before and there’s a chance that they’ll break not just the daily record, but the all-time record for the month of May. This is less likely although not impossible.
As climate change progresses, experts project that periods of extreme heat are likely to increase. From 1971 to 2000, the average summer in Massachusetts saw four days over 90 degrees. By mid-century, climate scientists say the state may have 10-28 days over 90 degrees each year. By the end of the century, Massachusetts could experience between 13 and 56 days of extreme heat each summer, depending on what steps are taken now to decrease greenhouse gas emissions.
The last time we had two back-to-back days of 90 degree weather in May was in 2017. This round of heat will not qualify as a heat wave, as you need 3 days in a row of 90 degree temperatures for that criteria to be met.
A heat advisory is posted across Southern New England. This is because when you combine the actual temperature with the humidity it will feel in the mid to upper 90s both afternoons. A sneaky sea breeze might keep things cooler at Logan Airport Sunday, this is tough to predict, but could occur.
As far as records go, the daily high-temperature record for Boston both days is 93 degrees with the all-time record for the month of May of 97 degrees set way back in 1880. You can see the other records below. There’s a chance any of these could be tied or broken with the highest temperatures likely on Sunday.
You would think we might see some showers between the heat and a return to more seasonable levels Sunday night and Monday, but the chances for any showers or thunderstorms are actually quite low. By the middle of next week, readings will be back to the 60s at the coastline with a cooler sea breeze.