donsutherland1

Hopefully, a corrected figure will be provided.

Clouds were breaking across the region this afternoon as the rain of yesterday into this morning had departed. Rainfall amounts included: Bridgeport: None Hartford: 1.52" Islip: 0.38" New Haven: 0.81" New York City-Central Park: 0.78" New York City-JFK Airport: 1.03" New York City-LaGuardia Airport: 0.53" Newark: 0.68" Philadelphia: 0.14" Poughkeepsie: 1.23" White Plains: 1.21" It will turn warmer tomorrow. High temperatures will top out mainly in the lower 80s tomorrow through the weekend. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. There will be higher-than-climatological risk of at least one period in September with highs in the upper 80s or perhaps 90s. Summers similar to the current one have had September highs of 90 or above about 10 percentage points above that for all other years. The ENSO Region 1+2 anomaly was +0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.53°C and the ENSO Region 3.4 anomaly has averaged -0.20°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was +1.33 today. The preliminary Arctic Oscillation (AO) was -0.858 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 88% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 74.4° (1.7° below normal). Supplemental Information: The projected mean would be 0.8° below the 1981-2010 normal monthly value.

My list was developed based on four criteria for which data is widely available: 1. Mean temperature 2. Highest maximum temperature 3. Highest minimum temperature 4. Number of 90F/32.2C or above high temperatures These values were standardized (standard deviations from the historic mean values for the period of record) I ran the numbers weighting each of the four criteria equally (initial approach) and also placing 50% weight on the mean temperature and then allocating the remaining 50% weight equally among the remaining three criteria. Further, I ran these numbers for a true summer (June-August) and extended summer (June-September) scenario. The different approaches were utilized based on various comments and "what if" questions made in the thread. If asked, I lean toward the second approach to weights (50% weight for the mean temperature as opposed to equal weights for all criteria) for the June-September period, as even relatively cool summers can have a short bout of extreme heat. Weighting everything equally skews the values. Separately, but not posted, I also looked at how much warming over the historic period has influenced summer mean temperatures. The coefficient of determination was 0.25, meaning that 25% of the variation in mean summer temperatures is explained by the ongoing warming and 75% is explained by internal variability. That's actually a quite high figure explained by warming, alone. Here's what summers look like at Central Park (1869-2024): Here's what they look like when the warming component is removed (as expected, the trend would be 0, but I included the trend line to illustrate that the warming was fully removed): In other words, here's what they would look like were internal variability, alone, responsible. Based on the data, Summer 2010 was just over 1.1F warmer than it would have been without the warming. Based on the internal variability, if a summer similar to 1876 occurs, the mean would be around 78.5F for the summer given the warming. It's probably a matter of time before the Summer 2010 figure is eclipsed (probably no later than the 2030s). Moreover, when it happens, the margin by which the record is broken could be fairly large, as one has seen elsewhere in recent years where summer records were broken.

Here they are: Bridgeport: 1953 Islip: None New York City-Central Park: 1921, 1931, 1953, 1983, 1993 New York City-JFK Airport: 1983 New York City-LaGuardia Airport: 1953, 1983, 2010, 2018 Newark: 1914, 1931, 1944, 1953, 1973, 1983, 1989, 1991, 1993, 2010, 2018 White Plains: 1953

For historical context, below is the distribution of highest temperature by month for NYC, JFK, LGA, and EWR.

Phoenix has a five-year master plan for expanding trees/shade. The City is aware of the growing risks its people face from increasingly frequent and intense heat. https://www.phoenix.gov/content/dam/phoenix/heatsite/documents/ShadePhoenixPlan_Nov13CouncilDraft_topost_EN.pdf

Most, but not all of the area is below normal so far. I suspect that the entire region will finish below normal once August concludes. NYC will be solidly below normal.

For Central Park, I included all summers from 1869-2024.

The temperature in Central Park has fallen to 59. August 2025 is the second consecutive August with at least one low temperature in the 50s. The last time that happened was August 2007 and August 2008.

The temperature in White Plains has now fallen into the 50s. That is the 7th day this month and the most during August 1-20 since 2013.

Phoenix is on track to record its fourth hottest summer on record. All four will have occurred since 2020. The ranking will be as follows: 1. 2024 2. 2023 3. 2020 4. 2025

11th June-August and 3rd if June-September is used.

The temperature peaked at 70° in Central Park. That was the coolest high temperature since June 17 when the high was 67°. Showers and periods of rain are likely into tomorrow. Most areas should see 0.50" or less of rain. However, some spots could see heavier rain. High temperatures will likely reach the lower and middle 70s tomorrow and then climb into the lower 80s on Friday through the weekend. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. There will be higher-than-climatological risk of at least one period in September with highs in the upper 80s or perhaps 90s. Summers similar to the current one have had September highs of 90 or above about 10 percentage points above that for all other years. The ENSO Region 1+2 anomaly was +0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.53°C and the ENSO Region 3.4 anomaly has averaged -0.20°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was -8.56 today. The preliminary Arctic Oscillation (AO) was -0.972 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 74.6° (1.5° below normal). Supplemental Information: The projected mean would be 0.6° below the 1981-2010 normal monthly value.

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A dramatic change to a sustained period of cooler weather has now occurred. High temperatures will likely reach the middle and upper 70s through Thursday and then the lower 80s on Friday through the weekend. Some showers or periods of rain are possible Wednesday afternoon into Thursday. Most of the region will see less than 0.50" or rain, though widely scattered areas of heavier rainfall are possible. The Jersey shore could see heavier rain and a gusty wind. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, rip currents, and some showers or periods of rain would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. There will be higher-than-climatological risk of at least one period in September with highs in the upper 80s or perhaps 90s. Summers similar to the current one have had September highs of 90 or above about 10 percentage points above that for all other years. The ENSO Region 1+2 anomaly was +0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.53°C and the ENSO Region 3.4 anomaly has averaged -0.20°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was -17.72 today. The preliminary Arctic Oscillation (AO) was -0.771 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 80% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 74.8° (1.3° below normal). Supplemental Information: The projected mean would be 0.4° below the 1981-2010 normal monthly value.

Yes, that’s correct. Phoenix has a pronounced UHI effect. One sees it particularly in the explosive increase in 90 or above low temperatures.

A dramatic change to a sustained period of cooler weather has now occurred. High temperatures will likely reach the middle and upper 70s through Wednesday and then the lower 80s on Thursday and Friday. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, and rip currents would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. There will be higher-than-climatological risk of at least one period in September with highs in the upper 80s or perhaps 90s. Summers similar to the current one have had September highs of 90 or above about 10 percentage points above that for all other years. The ENSO Region 1+2 anomaly was +0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.53°C and the ENSO Region 3.4 anomaly has averaged -0.20°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was -4.73 today. The preliminary Arctic Oscillation (AO) was -0.721 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 70% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 75.2° (0.9° below normal). Supplemental Information: The projected mean would be at the 1981-2010 normal monthly value.

A cooler regime is now in place and it will remain in place for an extended period of time. Here's where things currently stand with respect to select high temperature thresholds for 2025:

Those findings aren't too surprising. The UHI Effect grows most rapidly when an area first begins to urbanize. From 1950-1980, Phoenix's population grew 6.9% per year (Phoenix metro area: 6.4% per year). Since 1980, Phoenix's population has been growing 1.7% per year (Phoenix metro area: 2.7% per year). Since 2000, those rates have slowed further to 1.0% per year and 2.0% per year respectively. Phoenix's suburbs are currently growing faster than the City.

Central Park picked up 0.64" rain in an hour. While impressive, that was just half of the hourly record of 1.28" for August 17 that was set in 1974.

I've often noted that Phoenix's warmth is a combination of UHI and climate change. The scientific literature describes numerous impacts on the Southwest monsoon in a warmer climate, particularly a drier monsoon season, fewer rain events, and higher temperatures during monsoon season. This evolution is currently in its early stages. The outcome described in the literature won't happen all at once or uniformly. Phoenix deserves focused attention because it represents both an extreme case and an early signal of how climate change and aridification interact in the desert Southwest. Phoenix’s accelerated warming, even as UHI amplifies the impact of ongoing warming, makes it a valuable barometer of what other communities may face as aridification deepens across the state.

Today saw hot temperatures across much of the region. Highs included: Bridgeport: 88° Islip: 86° New Haven: 89° New York City-Central Park: 91° New York City-JFK Airport: 85° New York City-LaGuardia Airport: 91° Newark: 94° White Plains: 89° A dramatic change to a sustained period of cooler weather now lies ahead. A cold front will cross the region this evening or tonight bringing some showers or thundershowers. In the wake of the frontal passage, noticeably cooler air will overspread the region. High temperatures will likely reach the upper 70s Monday through Wednesday and then the lower 80s on Thursday and Friday. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, and rip currents would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. The ENSO Region 1+2 anomaly was +0.8°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged -0.15°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was +4.49 today. The preliminary Arctic Oscillation (AO) was -0.220 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 66% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 75.4° (0.7° below normal). Supplemental Information: The projected mean would be 0.2° above the 1981-2010 normal monthly value.

Yes. I ran the numbers this morning to see what the coefficient of determination was. It is .0.0143. This was even lower than I had thought when I had run the scatter diagram earlier today.

When it comes to ACE and winter temperatures (using NYC), the long-term warming already overwhelms the ACE. Here's what it looks like (anomalies are against the Winter 1869-70 through 2024-25 mean temperature for purposes of standardization): Here's what happens when one detrends the data for the ongoing warming (takes out the warming signal):