ITHACA, N.Y. — It’s the first week of climatological summer and it will certainly feel that way in Ithaca and Tompkins County, as hot, humid and stormy conditions will prevail over the next several days thanks to moist flow on the backside of a ridge of hot air. However, the flow will switch to a more northerly tap later in the week, with more seasonable and comfortable conditions by next weekend.
May 2021 is going down in the record books as a rather cool month compared to the local climatology. According to the Northeast Regional Climate Center based out of Cornell’s campus, the Game Farm Road weather site in Dryden recorded an average temperature last month of 54.3°F, which is 1.3°F below normal for the month of May. That’s below average, but not especially unusual; 54.3°F is only 40th coldest in the 129 years of Ithaca-area records.
Generally speaking, the further east one was last month, the warmer it was relative to normal. 23 stations were below normal, and 12 were above normal, and three (Portland, Maine, Boston, and Bridgeport, Connecticut) had top 20 warmest Mays. Albany was by far the coldest, but the data is poor quality because the temperature sensor at the Albany airport has a cold bias and has yet to be replaced even though the faulty one was installed over a year ago.
On the precipitation side, the Game Farm Road weather station read 4.05″ of rain (and no snow), well above the 3.20″ typically seen at the site during the month of May. Once again, this was no an extreme month; it was 38th wettest recorded for Ithaca. Much of this can be tied into the powerful coastal storm that whipped the region over Memorial Day weekend – where May was a wet month pretty much coincides with where the bands of the storm hit hardest. To the north and to the south of that storm’s bands, areas were much drier than normal.
Regionally, those variations were significant. Four of the 22 drier-than-normal sites ranked this past May were among their top 20 driest on record, with Burlington the most extreme with their 12th driest May on record. On the other end of the spectrum, six of the 13 wetter-than-normal sites ranked this May among their 20 wettest on record, including Binghamton with 10th wettest.
It’s warmed back up this weekend, with heat and some amount of humidity on the back side of a strong ridge ushering warm, marginally moist air into the region. Generally speaking, it’ll be an above-normal week temperature-wise, with precipitation dependent on the frequent bouts of thunderstorms that will make for a real scattershot performance on whether an area if wetter or drier than normal.
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With temperatures in the low to mid 90s, normally this is when we start to roll out the heat advisories, expecting a heat index to make it feel warmer than the temperature reading, and potentially put our more cold-adapted selves at risk in the heat.
However, the heat index is largely a non-factor today, it’s very close to the actual temperature. This is because the heat index is dependent on humidity, and it’s just not humid at the moment, in the lower 60s for dewpoint – noticeable, but our traditional definition if muggy is more like the upper 60s, with oppressive and dangerous heat indexes more likely with dewpoints above 70°F. A stable layer in the lower to mid levels of the atmosphere is not only keeping dewpoints restrained, it’s also inhibiting shower and thunderstorm development, so while it will be mostly cloudy at times, it will remain dry for the remainder of your Sunday. Tonight will be mostly clear and quiet, and good for you stargazers out there, with lows in the mid 60s.
The humidity will begin creeping up Monday as the flow around the ridge takes a more southwesterly angle, which will advect more humid air from around the Gulf of Mexico into the Southern Tier. With a more unstable atmosphere brought on with that humidity and weak short wave (pulse of instability) passing through, expect some pop-up showers and thunderstorms from late afternoon through evening, some of which could be strong given the ample heat energy and potential atmospheric dynamics in play. Otherwise, expect increasing clouds through the day with highs will be in the upper 80s to low 90s. Monday night will be mostly cloudy and humid with lows around 70°F.
As the flow from the Gulf of Mexico. becomes more direct Tuesday, it’ll be hazy, not and humid. The dewpoint will be in the low 70s, and it will feel oppressive outside. Even though highs will be in the mid 80s, the heat index will be in the mid 90s. It will be a very unstable atmosphere, and by late morning there will be enough heat energy rising from the surface to fire up the first of what will likely be several rounds of showers and thunderstorms during the day, with mostly cloudy skies in between. The storms will continue into the night Tuesday, with some tapering off after midnight. It will be mostly cloudy otherwise, with lows in the upper 60s.
Wednesday is likely to be another hot and humid day, if maybe slightly less humid than Tuesday. Otherwise, expect more of the same, with partly to mostly cloudy skies and scattered showers and thunderstorms rumbling across the region throughout the day. Highs will once again be in the mid 80s with a heat index into the low and mid 90s. Wednesday night will see some slight effects from a high pressure system to the north, which should allow for a little drying and cooling, with partly cloudy skies, mid 60s and a few scattered shower overnight.
Thursday will be a little less humid with dewpoints in the mid 60s, but still sees that active convective weather pattern during the day. With highs in the mid 80s, partly cloudy skies will occasionally be interrupted by showers and weak thunderstorms. Thursday night sees a greater northwesterly component in the overall flow aloft, which will allow for a little more cooling, with lows around 60°F and mostly cloudy skies.
Friday will be substantially cooler as the local upwind flow around the ridge changes over from southwest to more west-northwest. Highs will only be in the upper 70s, with a few weak showers later in the day and mostly cloudy skies otherwise. Friday night will host a chance for a few rain showers, mostly cloudy skies, and lows in the low 60s.
Next weekend is looking seasonably warm with the chance for a few widely scatted rain showers Saturday, but dry otherwise. Highs both Saturday and Sunday will be in the upper 70s and low 80s, with dewpoints in the upper 50s to lower 60s, so a touch humid at most. Lows will be in the low 60s overnight.
Looking ahead to the middle of the month, a ridge will be building over the Mountain West and that should result in warmer temperatures over the western half of the United States, with a downstream trough that will likely result in cooler than normal conditions for the Northeastern United States. Alongside those cooler temperatures, drier than normal conditions should be expected across the northern half of the country.