mjr

Central Park NYC is designated by the World Meteorological Organization (WMO) as a Centennial Observing Station. Mandatory criteria for recognition include, among others, 1. The station was founded at least 100 years ago. 4.Any known observing station relocation or change in the measurement technique have not significantly affected the climatological time-series data. 8. The observed and measured data shall be subject to routine quality control procedures according to current WMO guidelines and practices. These include strict measurement and instrumentation guidelines. I submit that NYC is not in compliance with guidelines 4 and 8 and the WMO should either insist that something be done or remove the Centennial Observing Station designation. Of course, since the site was moved in 1996, the historical record has been irreparably damaged.

In 2025, NYC reported 14 days of 90 or above, pretty much bringing up the rear of the list of stations used for comparison on this site. While most of these locations are in NJ and less susceptible to marine influences, the other NYC stations showed LGA with 26 days and even JFK reported 15. ISP was not far behind. For a broader comparison, one need only look at New England. Bostn had 19 days, and BDR, the usual hot spot because of its topography, had 24. However, HVN, right on the south shore, reported 15 days and BDR, practically in Long Island Sound, reported 15 as well. This might have been the first time that BDR actually exceeded NYC. In the past, the comparisons were between NYC, LGA and EWR. In 2025, at least, they were NYC, JFK, ISP and BDR. We may soon need to be looking at Nantucket.

In 1962 it was in May and in 1976 it was in April.

Going forward, whether it is later this summer or in future years, whenever a potential heat wave in is the forecast, all the news stories will continue to propagate the misleading statement that "NY City has not reached 100 degrees since 2012."

Apart from time series comparisons is the issue of comparing NYC weather and climate with other locations and regions and also describing NYC summer weather characteristics to the general public. In the interest of simplicity, summer weather is frequently measured by the number of days which exceed 90 degrees while other factors, such as high minimum temperatures, are basically ignored. Recently, a top meteorologist at a leading weather service provider was giving his summer forecast and it was based on the number of 90 degree days. If I remember correctly he used 16 days as average for NYC while the corresponding figures for other cities were 14 for Boston, 30 for Philly and 40 for DC. While it is certainly true that PHL and DCA have higher summer maxima, this gives the misimpression that overall summer conditions for NYC (usually interpreted as Manhattan) and Boston are largely indistinguishable. Of course you can blame the one dimensional criterion that he used but the thermometer siting is certainly a nontrivial factor. Just as an aside, when comparing NYC to other locations, an overwhelming number of observations are taken in airport or urban environments so maybe concrete is a more useful comparison.

Probably should not get carried away with prospective 90+ readings at NYC as we now seem to be well into the "Central Park Foliage " season during which the NWS has abandoned any pretense of caring about accurate afternoon temperature readings at NYC. Below is for 2024. Average High Temperature Feb Mar Apr May May 20-31 June 1-8 EWR 47.4 56.5 63.6 75.2 81.7 85.4 LGA 45.6 54.3 60.8 72.3 79.1 82.9 NYC 46.2 55.7 63.8 72.5 78.4 80.9

Having a hard time finding historical lists of annual 90+ days for various stations, for example LGA, EWR, BOS, DCA, with LGA being a proxy for the NY metropolitan area. While there is no question that BOS<LGA<DCA, I'm wondering if there have been any years in which either part of the inequality didn't apply (Central Park is a different story). While it seems to apply so far in 2022, it would be interesting if artificial local anomalies (tree canopy or Newark hot spot as opposed to proximity to ocean) are able to overwhelm climatological norms this year so that EWR would have more 90+ days than DCA while NYC would have fewer than BOS in the same year. After a slow start BOS has been gaining on NYC. Of course, number of 90+days is one dimensional and totally misleading but that is the benchmark that everyone uses.

Great idea...problem solved.

Backdoor cold fronts suck. They can happen at any time of the year. I believe that the geography of LI Sound helps funnel NE winds into NYC and propels some of these fronts through when one might expect them to remain to the east of us. Also, I feel that this makes it more difficult for them to return through NYC as a warm front. I have been frustrated at forecasts predicting sunny 80 degree temps only to spend the day in the 50s while central NJ gets up to 80. I have no evidence to back this up but it seems to me that these fronts frequently occur in situations that feature an upper level eastern ridge. Upper level eastern ridges can translate to surface highs over Eastern Canada which send down backdoor fronts. I am also pretty pessimistic about EWR reaching 70 Tuesday unless we experience unexpected afternoon breaks of sun.

September will end up with a mean temperature above 70, probably around 70.3. The Central Park thermometer tried its best to make sure that it would not happen but the month ended one day too early. A few weeks ago someone was going to write a letter concerning the foliage issue to the powers that be. I wonder if anything ever came of that. w

Very interesting research. I have always considered the C-D boundary to extend from St. Louis to NYC, roughly following the Ohio river. Amazing how changes of a fraction of a degree can put you in a completely different climate zone. I guess the line has to be drawn somewhere, though. When I looked at the Britannica article, though, it struck me that on the map, the Eastern seaboard of the US could not be based on a 26.6F demarcation. I dug a little deeper and it turns out that the map is based on a 2007 revision which does, in fact, use 32.0F. Thanks for sharing this.

A south wind at JFK comes directly off the cool ocean (about 1500 miles of it). At Newark, even a south wind with no westerly component, travels over about 50 miles of land. Places like LGA and NYC are far enough away from the ocean so that they can experience significant daytime heating even if an afternoon sea breeze eventually cuts it off. During the spring there can be times when the temperature difference between Newark and JFK can be 20 degrees or more. La Guardia underperforms if the wind direction is from the NE or ENE coming off Long Island Sound. Central Park underperforms if the trees have leaves on them. Interestingly, the Boston airport station is also directly on the ocean but there the ocean is to the east. Thus, a south or southwest wind at Boston will allow for hot temperatures and a west wind even hotter because of a downslope effect. However, a wind from the north through the east (or, alternatively, a light pressure gradient allowing for an afternoon sea breeze) will result in unpleasantly chilly temperatures. Geography is destiny.

At this time of year, under the right conditions, the high sun angle and dry ground can cause a hot air mass to be created in the Northern Plains without the need for the heat to be advected from the south. More southern areas may possibly be less extreme because of clouds, precipitation or whatever. This hot northern airmass can eventually be transported eastward to northern New England and Quebec. In this scenario, the heat goes from west to east and not from south to north.

Excellent.