TheClimateChanger

Looking solely at minima, this year was the highest on record by a full degree. That's a substantial deviation when you are considering a whole region. The mean regional minima was 61.4F this year - an astounding 6.1F above the 20th century mean! Prior to 2013, there had never been a July with a mean minimum in excess of 60F.

Hottest month on record in New England as a whole, and yet we have posters from New England on here calling it the year without a summer. Go figure. Incredibly, 4 of the top 10 hottest Julys on record in New England have occurred within the last six years, and both of the top 2 within the last four years. By comparison, only 3 of the top 10 hottest Julys date back to the 111-year period from 1895 and 2005.

July 2023 was the 11th hottest July on record in the United States. Maine, Florida, Arizona, and New Mexico all experienced their hottest July on record, with an additional 8 states seeing a top five warmest month. Only 5 states - all in the upper midwest - were significantly below the average. The only non-21st century years with hotter Julys than this nationally were 1936, 1934, 1901, 1931, and 1980 [the latter two by less than one tenth of a degree]. So while we may not have been quite as hot as other parts of the globe, it certainly wasn't a mild month by any stretch of the imagination in the U.S.

July finished up as the 11th warmest nationally, and 27th warmest in the Commonwealth. It was the hottest July on record in Arizona, New Mexico, Florida and Maine. Delaware, California, Texas, Louisiana, Connecticut, Massachusetts, Vermont, and New Hampshire, also had Top 5 warmest months, while Nevada and Utah just missed that metric (finishing in 6th place). Only 5 states (Minnesota, Iowa, North Dakota, South Dakota and Nebraska) experienced temperatures significantly below the median year.

Some data from downtown Toronto: July 1841: July 1842: July 1865: July 1868:

Here's what Lansing, Michigan (one of my reference cities for data back to 1863) looked like in July 1865, just to get a flavor of some of these months: Conversely, here is July 1868 at Lansing:

Here is my chart for the lower Great Lakes region for the month of July. Top 5 warmest years: 1921, 1868, 1955, 2012, 2020 Top 5 coolest years: 1891, 1865, 1841, 1842, 1837

Unreal how it's only a fraction of a degree warmer than DTW despite basically being in Kentucky.

Not gonna lie. This would be pretty epic.

Thought we might make a run at 90 today, given it was 87 before 1 pm. Looks like clouds and isolated showers will prevent that from happening.

Lots of red and orange on this map.

Will be interesting to see whether Dayton accumulates another 90 degree day today. 5-minute observations show a number of 90F readings, but, due to rounding issues, that does not guarantee a high of 90F.

On 90-degree watch today. Up to 88 on the 5-minute observations. Can we eek out the third 90+ of the year?

Sorry, for off-topic, but I wasn't the one who brought up Chile. Just for additional context, here are the records for La Serena, Chile in the Coquimba region where the heat has been most pronounced. While average highs are lower this time of the year, some of the warmest readings on record have occurred in the wintertime. In general, it's a very temperate location that has never exceeded 28.5C. So while the intensity of the heat is very impressive, and perhaps unprecedented, the fact that it's occurring in the middle of winter is not particularly noteworthy. These areas do not experience winters like we do here in the United States. Instead, it's only a little bit cooler than summertime but with more daily variability.

I don't think those areas have nearly the seasonal variations that we do. Nevertheless, some areas have reached all-time record highs, so it is certainly way out of the norms either way (as evidenced by those ECMWF maps showing 20C + anomalies in spots). It appears some of the extreme warmth is being driven by Foehn winds, also known as Chinook winds in North America (i.e., extreme compressional heating downwind of the mountain peaks).

Unofficial data for the period 1830-1870 is available in the 1943 Annual Weather Review for MDW. It is based on records of the War Department at Fort Dearborn on Wacker Drive in present-day downtown Chicago, records of the Smithsonian Institution in various parts of the city, with some interpolation of missing data by other observations outside the city. Note that temperature means during this era were generally taken as the average of three measurements (typically 7am, 2pm, and 9pm), which tends to have a small warm bias compared to the average of maximum and minimum. This warm bias is most significant in the summertime. Recall this predates daylight saving time, and time zones, at least in the early part of that period. So these would have actually been observed after 8 am in the summertime [perhaps as late as 8:30, 8:45 if prior to standardized time zones], and would have been several degrees above the actual low. The inclusion of the 9 pm [actually equivalent to readings taken at 10 pm or later in the summertime during modern daylight saving time] reading somewhat mitigates this effect, but does not entirely eliminate it.

You can always pull up the station histories from the monthly and annual weather reviews under Local Climatological Data (LCD) on the NCDC Image and Publication System: https://www.ncdc.noaa.gov/IPS/lcd/lcd.html These also tell exactly when the extreme thermometers were replaced with hygrothermometers, as well as the elevation of all of the instruments above ground level (and the elevation of the observation site above sea level). For example, here is the station history in the 1979 annual summary for MDW: And in the 1987 annual summary for ORD:

Very impressive. From Dr. Spencer:

July temperatures at Grand Canyon National Park Airport and Phoenix, from 1996-2023. There may be a small UHI component to the warming trend, but it's still clearly warming very rapidly even in places where nobody lives. Grand Canyon N.P. - Warming at 9.9F/century since 1996 Phoenix - Warming at 12.2F/century since 1996

Not sure yet where June & July two-month period will fall, but Ryan Maue says July will be 10-12th warmest in the rankings nationally. Looking at the list, only 1936, 1934, 1901, 1931 & 1980 were the only pre-21st century years with hotter Julys than this year nationally.

And holy cow - a 35C diurnal temperature range. Wow.

All time high for Coquimbo province, in the middle of winter:

Yes, primarily aloft today. The NWS Pittsburgh AFD does, however, suggest some may mix down to the surface tomorrow. Not sure if this will impact central PA though.

Doubtful. You observed only a 13.7F diurnal range in July. That has to be the smallest diurnal range on record, no? I would argue that is an unnatural climate for anywhere in Pennsylvania. Even adjacent to Lake Erie, the diurnal range in Erie is typically larger than that. Philadelphia, in the core of the urban heat island, had a diurnal range of 16.7F. I have my doubts that a diurnal range that small is possible in a summer month in Pennsylvania, without some sort of external influence on the temperature.