2c:null 2d:["$","title",null,{"children":"The Worst (Hottest) Waco September Ever | Gideon Jeffrey | Observable"}] 32:T50c,allSeptemberDailyHighs = Plot.plot({ marks: [ Plot.line( septemberACTDaily.filter(d => d.YEAR.getUTCFullYear() < 2026), { x: "DAY", y: "TMAX", z: "YEAR", stroke: "darkgrey", strokeOpacity: 0.7, strokeWidth: 1 } ), Plot.line( septemberACTDaily.filter(d => d.YEAR.getUTCFullYear() >= 1996 && d.YEAR.getUTCFullYear() < 2026), Plot.groupX( { y: "mean" }, { x: "DAY", y: "TMAX", stroke: "#1f78b4", strokeWidth: 4 } ) ), Plot.line( septemberACTDaily.filter(d => d.YEAR.getUTCFullYear() == 2026), { x: "DAY", y: "TMAX", stroke: "red", strokeWidth: 4 } ), Plot.ruleY([50]), ], width: 850, y: { domain: [50, 110], label: "Temperature (°F)" }, x: { label: "Day of September", labelAnchor: "center", ticks: d3.range(1, 31) }, color: { legend: true, type: "categorical", domain: ["Individual years, 1941-2025", "Previous 30 year average", "2026"], range: ["darkgrey", "#1f78b4", "red"], fontSize: 14 }, style: { fontSize: 12 }, margin: 40, title: "Daily high temperatures in September in Waco, 1941-2026" })33:T759,septemberDailyHighPlot = ({ marks: [ Plot.line( septemberACTMonthly, { x: "YEAR", y: "MONTHLYAVGTMAX", stroke: "url(#gradient)", strokeWidth: 2.5, title: (d) => `${new Date(d.YEAR).toLocaleDateString('en-US', { timeZone: 'UTC', year: 'numeric' })}\n${d.MONTHLYAVGTMAX} °F` } ), Plot.ruleY( septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTMAX), { stroke: "#800026", strokeDasharray: "5,2", strokeWidth: 2 } ), Plot.text( [{ y: septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTMAX), label: "2026: " + septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTMAX) + " °F"} ], { y: "y", text: "label", dy: 10, textAnchor: "start", fontSize: 12 }), Plot.ruleY([76]), (_index, { y, color }) => htl.svg` ${d3.ticks(0, 1, 10).map( (t) => htl.svg`` )}` ], x: { labelAnchor: "center", label: "Year", type: "band", ticks: d3.utcYear.every(10), tickFormat: "%Y" }, y: { domain: [76, 100], nice: true, grid: true, label: "°F" }, color: { scheme: "YlOrRd", legend: true, label: "Average Daily High (°F)", domain: [76, 100] }, width: 850, style: { fontSize: 12 }, marginBottom: 40, marginTop: 40, title: "September monthly average highs, 1941-2026", subtitle: "Observations from station USW00013959 (Waco Regional Airport)" })34:T75f,septemberDailyLowPlot = ({ marks: [ Plot.line( septemberACTMonthly, { x: "YEAR", y: "MONTHLYAVGTMIN", stroke: "url(#gradient)", strokeWidth: 2.5, title: (d) => `${new Date(d.YEAR).toLocaleDateString('en-US', { timeZone: 'UTC', year: 'numeric' })}\n${d.MONTHLYAVGTMIN} °F` } ), Plot.ruleY( septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTMIN), { stroke: "#4ef66a", strokeDasharray: "5,2", strokeWidth: 2 } ), Plot.text( [{ y: septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTMIN), label: "2026: " + septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTMIN) + " °F"} ], { y: "y", text: "label", dy: 10, textAnchor: "start", fontSize: 12 }), Plot.ruleY([60]), (_index, { y, color }) => htl.svg` ${d3.ticks(0, 1, 10).map( (t) => htl.svg`` )}` ], x: { labelAnchor: "center", label: "Year", type: "band", ticks: d3.utcYear.every(10), tickFormat: "%Y" }, y: { domain: [60, 80], nice: true, grid: true, label: "Temperature (°F)" }, color: { scheme: "cool", legend: true, label: "Average Daily High (°F)", domain: [60, 80] }, width: 850, style: { fontSize: 12 }, marginBottom: 40, marginTop: 40, title: "September monthly average lows, 1941-2026", subtitle: "Observations from station USW00013959 (Waco Regional Airport)" })35:T763,septemberAvgPlot = ({ marks: [ Plot.line( septemberACTMonthly, { x: "YEAR", y: "MONTHLYAVGTEMP", stroke: "url(#gradient)", strokeWidth: 2.5, title: (d) => `${new Date(d.YEAR).toLocaleDateString('en-US', { timeZone: 'UTC', year: 'numeric' })}\n${d.MONTHLYAVGTEMP} °F` } ), Plot.ruleY( septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTEMP), { stroke: "#a11202", strokeDasharray: "5,2", strokeWidth: 2 } ), Plot.text( [{ y: septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTEMP), label: "2026: " + septemberACTMonthly.filter(d => d.YEAR.getUTCFullYear() == 2026).map(d => d.MONTHLYAVGTEMP) + " °F"} ], { y: "y", text: "label", dy: 10, textAnchor: "start", fontSize: 12 }), Plot.ruleY([70]), (_index, { y, color }) => htl.svg` ${d3.ticks(0, 1, 10).map( (t) => htl.svg`` )}` ], x: { labelAnchor: "center", label: "Year", type: "band", ticks: d3.utcYear.every(10), tickFormat: "%Y" }, y: { domain: [70, 90], nice: true, grid: true, label: "°F" }, color: { scheme: "turbo", legend: true, label: "Average Daily Temperature (°F)", domain: [70, 90] }, width: 850, style: { fontSize: 12 }, marginTop: 40, marginBottom: 40, title: "September monthly average temperature overall, 1941-2026", subtitle: "Observations from station USW00013959 (Waco Regional Airport)" })36:[{"id":"5bafbe7bb9d3db2de30dc516309ddfeccd117f2d8f5e98b7bf213408ce93374ec919be5d8f356a718562cab09c0b76203a6a16a7d28d11847070bca4f31e84f8","href":"https://static.observableusercontent.com/files/5bafbe7bb9d3db2de30dc516309ddfeccd117f2d8f5e98b7bf213408ce93374ec919be5d8f356a718562cab09c0b76203a6a16a7d28d11847070bca4f31e84f8","name":"september_act_averages.csv","type":"text/csv","lastModified":1791423992000,"size":6393},{"id":"6e062d5f74f66ef43adf12757811f066ff56afc21ff09478909f69b7720a0755dc59e72c4ecee7f74025d66cbbe4b144878d2534e61750c41a39f36d800b784d","href":"https://static.observableusercontent.com/files/6e062d5f74f66ef43adf12757811f066ff56afc21ff09478909f69b7720a0755dc59e72c4ecee7f74025d66cbbe4b144878d2534e61750c41a39f36d800b784d","name":"september_act_daily.csv","type":"text/csv","lastModified":1791423996000,"size":265022}] 30:{"id":"f0efb535263903de","slug":"hottest-waco-september-ever","title":"The Worst (Hottest) Waco September Ever","thumbnail":"965d7e7beb7c1c242bc937f2c62d4e2693677b966f28a9006329e48d624d6411","access_level":"public","create_time":"$D2026-10-03T15:57:42.943Z","update_time":"$D2026-10-08T16:29:21.748Z","view_time":null,"first_public_time":"$D2026-10-08T02:15:12.260Z","has_unpublished_edits":null,"fork":false,"stars":0,"starred":false,"owner":{"type":"team","id":"030c90355475f8d1","login":"gideonkylejeffrey","name":"Gideon Jeffrey","avatar_url":null,"tier":"starter_2024","bio":""},"version":732,"publish_version":732,"role":null,"authored":false,"authors":[{"type":"individual","id":"55b53f565c15d32f","login":"gideonkylejeffrey","name":"Gideon Jeffrey","avatar_url":null,"tier":null,"bio":""}],"members":[{"type":"team","id":"030c90355475f8d1","login":"gideonkylejeffrey","name":"Gideon Jeffrey","avatar_url":null,"tier":"starter_2024","role":"editor"}],"comments":[],"custom_thumbnail":true,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":null,"type":"notebook","body":{"titling":"auto","title":"The Worst (Hottest) Waco September Ever","cells":[{"id":1,"value":"# The Worst (Hottest) Waco September Ever\n_October 7th, 2026_\n
\n
","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":2,"value":"viewof displayedMetric = Inputs.select(\n new Map([\n [\"Average September high (°F)\", \"max\"],\n [\"Average September low (°F)\", \"min\"],\n [\"Average September temperature (°F)\", \"avg\"],\n [\"Total September highs >= 100°F\", \"hundredHighs\"],\n [\"Total September lows >= 75°F\", \"seventyfiveLows\"]\n ]),\n {\n label: \"Choose Metric:\",\n value: \"max\",\n width: 300\n }\n);","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":23,"value":"Plot.plot(topPlots[displayedMetric])","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":5,"value":"From my perspective, September weather in Central Texas is pretty much always “the worst.” I was born more than two thousand miles to the northeast in Canada, near the capital Ottawa. More than twenty years after moving to the southern United States, I still _imagine_ September as what childhood me experienced - genuinely chilly nights, days around 20 °C (68 °F), classic “fall is in the air” weather. Unfortunately for me, September in Waco is just August 2.0: Death Furnace Continued.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":6,"value":"For that reason, me claiming that any September is “the worst” should be taken with more than a few grains of salt. But _this_ time, I'm right! After pulling 86 years of climatological observations from the Waco Regional Airport, available through the NOAA’s Climate Data Online service, I can confirm that September 2026 in Waco was the hottest ever. In fact, out of all Septembers from 1941 to the present, this past September had:","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":7,"value":" - The highest average daily high temperature (99.3 °F, almost 2 full degrees higher than the previous record of 97.9 °F set in 1977)\n - The highest average daily low temperature (75.3 °F)\n - The highest overall average temperature for September (87.3 °F)\n - The most days with a high of at least 100 °F (16, shattering the previous record of 11)\n - The most days with a low of at least 75 °F (18)","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":9,"value":"To summarize: blistering heat during the day, no cooling off at night, repeating relentlessly.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":31,"value":"And on that point, _relentless_ was really what characterized this September's heat. There were no truly extreme temperatures by Texas standards - the high temperature didn't surpass 103 °F all month - but rather a continuous slog of very hot days. Here's another look at how each day's September highs in 2026 (red line) compare to all previous Septembers at Waco Regional Airport (grey lines) and to an average of the prior 30 years, 1986-2026 (blue line). Even though we didn't set many records, it's immediately noticeable how continuously we experienced _near_-record daily highs.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":30,"value":"$32","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":32,"value":"Thank goodness it's finally October!","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":10,"value":"If you want to explore the data further, September daily data and monthly averages are in the tables displayed below.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":35,"value":"### Daily","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":11,"value":"viewof septemberDetailTable = Inputs.table(\n septemberACTDaily,\n {\n layout: 'auto',\n columns: [\"DATE\", \"TMAX\", \"TMIN\"],\n header: {\n DATE: \"Date\",\n TMAX: \"Daily High\",\n TMIN: \"Daily Low\"\n }\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":36,"value":"### Yearly Averages","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":34,"value":"viewof septemberMonthlyTable = Inputs.table(\n septemberACTMonthly,\n {\n layout: 'auto',\n columns: [\"YEAR\", \"MONTHLYAVGTMAX\", \"MONTHLYAVGTMIN\", \"MONTHLYAVGTEMP\", \"DAYSTMAXATLEAST100\", \"DAYSTMINATLEAST75\"],\n header: {\n YEAR: \"Year\",\n MONTHLYAVGTMAX: \"Average High\",\n MONTHLYAVGTMIN: \"Average Low\",\n MONTHLYAVGTEMP: \"Average Temperature\",\n DAYSTMAXATLEAST100: \"Total 100+ °F Highs\",\n DAYSTMINATLEAST75: \"Total 75+ °F Lows\"\n }\n }\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":33,"value":"
\n
\n
\n\n### Code","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":12,"value":"septemberACTDaily = FileAttachment(\"september_act_daily.csv\").csv({typed: \"auto\"})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":14,"value":"septemberACTMonthly = FileAttachment(\"september_act_averages.csv\").csv().then((rows) =>\n rows.map((d) => ({\n ...d,\n YEAR: d3.utcParse(\"%Y-%m-%d\")(d.YEAR),\n MONTHLYAVGTMAX: parseFloat(d.MONTHLYAVGTMAX),\n MONTHLYAVGTMIN: parseFloat(d.MONTHLYAVGTMIN),\n MONTHLYAVGTEMP: parseFloat(d.MONTHLYAVGTEMP)\n }))\n)","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":18,"value":"$33","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":26,"value":"$34","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":27,"value":"$35","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":28,"value":"septemberHundredHighsPlot = ({\n marks: [\n Plot.barY(\n septemberACTMonthly,\n {\n x: \"YEAR\",\n y: \"DAYSTMAXATLEAST100\",\n fill: \"DAYSTMAXATLEAST100\"\n }\n ),\n Plot.ruleY([0]),\n ],\n x: {\n labelAnchor: \"center\",\n label: \"Year\",\n type: \"band\",\n ticks: d3.utcYear.every(10),\n tickFormat: \"%Y\"\n },\n y: {\n domain: [0, 20],\n nice: true,\n grid: true,\n label: \"Total Days\"\n },\n color: {\n scheme: \"ylorrd\",\n domain: [-5, 20]\n },\n width: 850,\n style: {\n fontSize: 12\n },\n marginTop: 40,\n marginBottom: 40,\n title: \"September days with high of at least 100°F, 1941-2026\",\n subtitle: \"Observations from station USW00013959 (Waco Regional Airport)\"\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":29,"value":"septemberSeventyFiveLowsPlot = ({\n marks: [\n Plot.barY(\n septemberACTMonthly,\n {\n x: \"YEAR\",\n y: \"DAYSTMINATLEAST75\",\n fill: \"DAYSTMINATLEAST75\"\n }\n ),\n Plot.ruleY([0]),\n ],\n x: {\n labelAnchor: \"center\",\n label: \"Year\",\n type: \"band\",\n ticks: d3.utcYear.every(10),\n tickFormat: \"%Y\"\n },\n y: {\n domain: [0, 20],\n nice: true,\n grid: true,\n label: \"Total Days\"\n },\n color: {\n scheme: \"cool\",\n domain: [0, 20]\n },\n width: 850,\n style: {\n fontSize: 12\n },\n marginTop: 40,\n marginBottom: 40,\n title: \"September days with low of at least 75°F, 1941-2026\",\n subtitle: \"Observations from station USW00013959 (Waco Regional Airport)\"\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":24,"value":"topPlots = ({\n max: septemberDailyHighPlot,\n min: septemberDailyLowPlot,\n avg: septemberAvgPlot,\n hundredHighs: septemberHundredHighsPlot,\n seventyfiveLows: septemberSeventyFiveLowsPlot\n})","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W36","stdlib":"2"}} 31:"$30:body"