Running Weather Today (Sat., Sept. 12): Boston 58°F, Chicago's 66° Dew Point, Austin Under a Heat Advisory to 111°F
Quick answer — Boston has the best running weather in the country this morning: 58°F at 7 a.m. with a 49°F dew point. Chicago is the same air temperature as an easy day in July once you read the dew point — 68°F over 66°F at the same hour. Austin is already 79°F before sunrise and lands under a Heat Advisory from noon, with the National Weather Service calling for a heat index up to 111°F.
What does each city feel like at 7 a.m.?
| City | 7 a.m. local | Dew point | Wind | The one thing that matters |
|---|---|---|---|---|
| Boston | 58°F, sunny | 49°F | 5 mph NE | Dry air. Singlet, and you will be cold for one mile. |
| New York | 63°F, sunny | 54°F | 2 mph NE | Almost no wind, so no evaporative help after mile 6. |
| Los Angeles | 69°F, patchy fog | 64°F | 5 mph SE | Fog holds to about 11 a.m., then 85°F by noon. |
| Chicago | 68°F, mostly sunny | 66°F | 5 mph SSW | 92% humidity. Sweat has nowhere to go. |
| Austin | 79°F, partly sunny | 75°F | 5 mph S | Heat Advisory from noon. Finish before 9. |
Which city has the best running weather this morning?
Boston, and it is not close. A 58°F reading with a 49°F dew point is the only start on this board where the air can still take your sweat. The Boston grid holds the city at 66°F through 10 a.m. and 73°F all afternoon, with the sea breeze picking up to 12 mph out of the southeast after lunch. If you have a long run banked for today and you live anywhere near the coast, go early and go long — our temperature-by-temperature kit guide puts 58°F squarely in shorts-and-singlet territory, with a throwaway layer for the first mile. Everything we run in this column lands on the daily weather page.
Why does 68°F in Chicago feel worse than 63°F in New York?
Dew point. Chicago sits at 66°F dew and 92% relative humidity at 7 a.m.; New York is 54°F dew and 72%. That 12-degree gap is the whole difference. Sweat cools you by evaporating, and evaporation slows as the air fills. Runners usually feel it above a 60°F dew point and notice it badly above 65°F. Chicago's dew climbs to 70°F by 10 a.m. even as the sun burns the humidity number down, so the late-morning air gets hotter without getting any drier: 77°F at 10, 84°F at 1 p.m., 86°F at 3. Marathon build-up runners stuck in that air should read the pace adjustment in our training notes before they judge today’s splits.
How late can you run in Austin today?
Not late. NWS Austin/San Antonio issued a Heat Advisory at 4:18 a.m. CDT covering the I-35 corridor and Coastal Plains from noon to 7 p.m., warning of temperatures up to 105°F and heat index values up to 111°F. The grid has Austin at 80°F at 6 a.m., 87°F by 10 and 95°F at noon. The dew point actually falls through the day, 76°F down to 67°F by late afternoon, which is why the air temperature can run away to 104°F at 5 p.m. A dawn start is the only comfortable option, and even that is a 75°F dew point.
What changes in New York tonight?
Rain, and a lot of it. NWS Upton has a Flood Watch up for New York City, southern Westchester and northeast New Jersey from late tonight through Sunday morning, with 1 to 2 inches of rain forecast and locally higher amounts. Showers and thunderstorms move in after dark. Sunday runners in Brooklyn, Manhattan or the Bronx should move the long one to the afternoon and expect standing water in the usual low spots. Reflective kit earns its keep on a wet, dark morning — we went through that in our fall visibility gear notes.
What about the Los Angeles fog?
It buys you two hours. Patchy fog holds downtown at 69°F through 8 a.m. and 73°F at 9, then breaks: 80°F at 11 a.m., 89°F by 2 p.m. with the dew point down at 62°F. Fog is not shade, though. The UV still gets through a thin marine layer, so sun cover matters even in the grey hour — a UPF top beats nothing.
Anyone racing today?
Plenty. Ten races are on the board across Saturday and Sunday, headlined by REVEL Big Cottonwood outside Salt Lake City and the Erie Marathon at Presque Isle tomorrow morning. Start-line numbers and entry status are in this weekend's race list, the hour-by-hour kit calls are in Friday's what-to-wear guide, and Erie gets its own course and weather-history preview. First-timers heading to a start line tomorrow should run the race-morning checklist tonight, not in the car. Shorter distances get their own coverage on the half and 5K page, and kit that survives a sticky start is in the gear index.
TL;DR — Boston 58°F over a 49°F dew point is the pick of the morning. New York 63°F and calm. Los Angeles 69°F under fog until 11. Chicago 68°F over 66°F dew, which is the hard one. Austin 79°F pre-dawn, Heat Advisory noon to 7 p.m., heat index to 111°F. New York gets a Flood Watch from late tonight into Sunday morning.
Sources
- Hourly temperature, dew point, wind and sky: National Weather Service gridpoint forecasts for Central Park (OKX), Boston (BOX), Grant Park Chicago (LOT), downtown Los Angeles (LOX) and Austin (EWX), retrieved Sept. 12, 2026, 7:40 a.m. ET.
- Watches and advisories: NWS active alerts for each point — Heat Advisory issued by NWS Austin/San Antonio at 4:18 a.m. CDT Sept. 12, and Flood Watch issued by NWS Upton at 2:20 a.m. EDT Sept. 12.
- Sale prices on fall running kit, checked separately by our sister desk: Activewear Deals.