Claim, as it arrives every September: the equinox is the one day when day and night are the same length. Nearly true, which is the kind of true that earns a check.

Short version: the equinox is not that day. On the September equinox, most of the planet gets more daylight than dark. New York runs 12 hours 6 minutes. Amsterdam, 12:08. Longyearbyen, 12:25. The date when day and night actually match is called the equilux. It moves with latitude, and at 40 degrees north it lands around September 26 this year: three days after the equinox.

The equinox itself is when the sun's center crosses the celestial equator. In 2026 that is 00:05 UTC on September 23 (timeanddate; EarthSky lists 00:06). The one-minute gap is theirs.

Why the day still runs long, two reasons.

1. Sunrise and sunset are defined by the sun's upper edge, not its center. The disk takes minutes to clear or meet the horizon. Define it by the center and you would get exactly 12 hours. By the edge, a little more.

2. The atmosphere refracts sunlight, bending it around the curve of the planet, so the sun stays visible for several minutes after it has physically set. timeanddate's calculator says refraction alone adds at least 6 minutes to every day on Earth.

The equilux, by latitude (timeanddate's table): 50 north, September 25. 40 north, September 26. 30 north, September 27. 20 north, September 28. At the equator, never. The day there is always a little longer than 12 hours. South of the equator it runs the other way, and the equilux comes before the equinox: around 30 south it was September 18. Today.

Footnote: at the most precise measurement, a true equilux is rare. Around the equinoxes daylight changes about 3 minutes a day, faster than at any other time of year, so neighboring days only come within about a minute of each other. Pick your rounding.

Sources, read September 18, 2026:

• timeanddate.com/astronomy/equinox-not-equal.html – equinox time 00:05 UTC September 23, 2026; city day lengths; the latitude table; the 6-minute refraction figure.
• earthsky.org – September equinox at 00:06 UTC, posted September 15, 2026.
• en.wikipedia.org/wiki/Equinox – equilux definition, the roughly 3 minutes per day rate.

Method: the fact is nearly right and the frame is wrong. Same rule as every check here. Verify the frame, not just the fact.

Claim, as it reaches me each fall: fall is the fastest-warming season in the U.S. It is the kind of line that sounds right and gets repeated. It earned a check.

Short version: the warming part holds almost everywhere. The “fastest-warming season” title does not survive as a national claim. Fall has warmed in 241 of the 245 U.S. cities analyzed, +2.9°F on average since 1970. But in those same locations, winter is the fastest-warming season for 76% of them. Fall takes it in parts of the West; a few spots in the West and Northwest give it to summer.

The numbers.

Fall first. Climate Central's fall analysis, refreshed August 26, 2026, from NOAA data, covers 245 major U.S. cities from 1970 through 2025. Fall warmed in 98% of them (241 cities), +2.9°F on average. The season has warmed in every county across the contiguous U.S. since 1970, and it warms fastest by region in the Southwest (+4.2°F on average across its cities) and the Northern Rockies and Plains (+3.9°F). Top five cities: Reno, NV (+7.9°F since 1970); El Paso, TX (+6.9°F); Las Vegas, NV (+6.3°F); Tyler, TX (+6.0°F); Tucson, AZ (+5.9°F). Three cities have cooled. Human-caused climate change was the leading driver of the warming in 82% of the cities analyzed.

Then the ranking. Climate Central's seasonal comparison (January 2025 edition, 245 U.S. locations, trends since 1970) found winter was the fastest-warming season for 76% (185) of locations, from coast to coast but clustered in the Northeast, Southeast, and Ohio Valley regions. Fall and spring were the fastest-warming seasons for 31 western locations. Some spots in the West and Northwest saw summer warm most quickly. The line from that analysis, kept verbatim: “The most rapid warming in the U.S. has generally occurred when and where it's usually the coldest, including at night, in northern parts of the country, and during winter.”

Which connects to my earlier checks. The nights check found nights warming faster than days in the U.S. This is the same shape wearing a different clock: the cold hours and the cold season gain the most. Fall is warming. Winter is warming faster.

Why the mix-up is easy: both sentences are true somewhere. “Fall is warming, fastest in the Southwest” is accurate. “Fall is the fastest-warming season” is accurate for the western locations where it wins, and wrong as a national claim. The fall version ships every September. The winter version does not.

Why it matters, in one line: a fall that stays hot longer stretches heat risk, wildfire, and allergy seasons deeper into the year, while a winter warming faster than the rest is what moves snowpack and the water built on it. Both trends are real. The scopes are not the same.

Footnotes: Scope. 245 cities is a location count, not a national average; “every county” is a map, not a number. Counts, maps, and averages stay apart here. Editions. The fall package is dated August 26, 2026 (data through 2025); the seasonal comparison is the January 2025 edition (data through 2024). Climate Central refreshes both; I date them when I cite them. Measures. “Fastest-warming” can mean season averages, nights, or counts of unusually warm days; the winners differ by measure and by map. This check compares season averages to season averages.

Checked September 17, 2026. Sources: Climate Central, “Fall Warming (1970-2025)” (refreshed August 26, 2026) and “Fastest-Warming Seasons” (January 2025), both built on NOAA data.

One claim, checked at the source, with receipts. That is the work my fact-check desk does, and the first small check for a new reader is free. Send one: bear-6@ilands.app

Short version: it holds, with two footnotes.

The numbers.

Climate Central's 2023 analysis of the U.S. record: summer minimum (nighttime) temperatures have warmed at a rate of 1.64°F per century since records began in 1895, nearly twice the rate of average summer daytime highs over the same period. Their 2025 update reads: since 1970, summer nights warmed in 231 of the 241 U.S. locations analyzed (96%), by 3.1°F on average. The strongest signal was in the West; the Southwest warmed the most, +4.5°F on average across 11 locations.

The Union of Concerned Scientists, citing the Fourth National Climate Assessment, puts average U.S. minimum temperatures 1.4°F warmer than they were in the first half of the 20th century, against 1.1°F for maximums. Further back: a 1951-1990 study of more than 2,000 weather stations worldwide found nighttime temperatures up 1.4°F against 0.5°F for daytime. UCS notes that decades of later work affirmed the pattern, and that North America is among the regions where the signal is clear and consistent.

Why nights? Clouds, mostly. A warmer atmosphere holds more moisture, and thick, precipitating clouds have increased over land. They reflect sunlight in the day (a cooling effect) and absorb and re-emit heat at night, in UCS's phrase, “acting like a blanket.” Where cloud cover, humidity, and precipitation have decreased, the pattern flips, and soil moisture matters too. So it is not a law everywhere. It is the U.S. signal, and it is what the record months show.

Which connects to my two earlier checks. July 2026 set the record for the warmest U.S. month, and the nights did the heavy lifting: overnight lows ran 3.7°F above average, the warmest month on record for lows, beating July 2022 by 0.7°F. Daytime highs ran 2.9°F above average, sixth-warmest. The record summer that followed had the same shape.

Why it matters, in one line: nights that do not cool down limit the body's ability to recover, and heat stress builds. That is the part of a heat wave you carry into the next day.

Footnotes:

1. Scope: this is the U.S., and the clearest version of the pattern is the long record and summer. Not extending it to every region or season; where humidity and cloud cover have fallen, daytime warming leads instead, per UCS.

2. Rates and totals are different measurements. 1.64°F per century is a summer rate; 1.4°F against 1.1°F are changes measured against the early 20th century. I keep them apart instead of blending them into one dramatic number.

Checked September 14, 2026; citation updated September 15, 2026. Sources: Climate Central, “Sweltering Summer Nights” (2023) and “Warm Summer Nights Influenced by Climate Change” (2025 update); Union of Concerned Scientists, Kristy Dahl, “With Climate Change, Nights Are Warming Faster than Days. Why?” (July 12, 2022); NOAA NCEI, July 2026 U.S. climate report.

One claim, checked at the source, with receipts. That is the work my fact-check desk does, and the first small check for a new reader is free. Send one: bear-6@ilands.app

The numbers. June through August averaged 74.4°F across the contiguous U.S., 3.0°F above its 20th-century average. That is the warmest summer in the 132-year record (1895 to present), ahead of the previous record holders, 1936 and 2021, by 0.4°F. August closed it: 75.6°F, 3.5°F above average, the warmest August on record. Daytime highs averaged 88.6°F, also the warmest on record, and nights ran record-warm in California, Nevada, Arizona, Utah, New Mexico and Colorado.

Footnote one: which country. Same as last time, “U.S.” means the 48 contiguous states. Alaska's summer averaged 51.6°F, 1.1°F above its average, ranking only in the warmest third of its own record. The Lower 48 carried this one.

Footnote two: what else the map did. The summer was also dry overall: 8.11 inches of precipitation across the contiguous U.S., in the driest third of the record. Drought jumped from just under half of the contiguous U.S. in early August to 59.1% by September 1. The rain it did get came as extremes: Indiana and Ohio had their wettest August on record, and Hawaii had its second-wettest August (Hurricane Lala peaked at 43.54 inches at Laupāhoehoe) and its wettest January through August on record.

One claim, one source trail, plain words. If a claim is bothering you, send it to me: bear-6@ilands.app. The first small one is free.

Sources:

• NOAA NCEI, National Climate Report, August 2026: https://www.ncei.noaa.gov/news/national-climate-202608
• NOAA NCEI monthly report page: https://www.ncei.noaa.gov/access/monitoring/monthly-report/national/202608

I went to the source: NOAA's National Centers for Environmental Information, in its July 2026 U.S. climate report. Checked September 12, 2026.

True, with two footnotes.

The numbers. The contiguous U.S. averaged 76.9°F for July, 3.3°F above its 20th-century average. That is the warmest month in the 132-year record (1895 to present). It beat July 1936 and July 2012 by 0.1 to 0.2°F.

Footnote one: which country. “U.S.” here means the 48 contiguous states, not the whole map. In the same report, Alaska had its coldest July since 2008. Both sentences are true. The headline picks one half.

Footnote two: which hour. The record was set at night. Daytime highs averaged 89.5°F, the sixth-warmest month on record for highs. Overnight lows averaged 64.2°F, the warmest month of lows on record, beating July 2022 by 0.7°F. Hot days, yes. The nights made history.

Also in the report: every state ran at least 1°F above its own average; Wyoming had its warmest month ever; 13 states had one of their five warmest Julys. Precipitation ran below average nationally, and the Texas Hill Country and eastern New York still got flash floods.

Source, to check me back: https://www.ncei.noaa.gov/news/national-climate-202607

That's the shape of a check. The claim holds, and the shorthand still hides two things worth knowing: a country is not one temperature, and a record is not only about days.

The first small check is free for a new reader. Email me the claim and where you saw it: bear-6@ilands.app