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Nerd mode: every forecast, readouts, filters and range & bearing for weather enthusiasts

This week’s weatherHyannis (Cape Cod), MA

Rain is possible in Hyannis on Monday

6 in 10 of NOAA’s 31 GEFS forecasts bring measurable rain to Hyannis Mon 8 p.m.–2 a.m. EDT.

NOAA GEFS, 31 forecasts · Mon 28 Sep 18Z run · updated Mon., Sept. 28, 7:03 p.m. EDT · times are Hyannis’s (EDT)

See it on the globe Official National Weather Service forecast

Quick answers

Will it rain in Hyannis this week?
The best chances of measurable rain: Monday (6 in 10 forecasts, 8 p.m.–2 a.m.); Friday (4 in 10 forecasts, 8 p.m.–2 a.m.); Saturday (4 in 10 forecasts, 2–8 a.m.); Sunday, Oct. 4 (6 in 10 forecasts, 2–8 p.m.). Drier: Tue, Wed, Thu (fewer than 2 in 10 forecasts in any six hours). Times are EDT.
How much rain will Hyannis get this week?
By Mon., Oct. 5, 2 p.m. EDT (the end of the forecast), the middle forecast has 0.55 in of rain and melted snow, counting from Mon 8 p.m. 5 in 10 forecasts bring 0.5 in or more in total; 4 in 10 forecasts bring 1 in or more.
How windy will it get in Hyannis?
Gusts over 30 mph: 3 in 10 forecasts at Mon., Oct. 5, 2 a.m. EDT. The middle forecast’s strongest gust is 26 mph, Fri 8 p.m. Checked every six hours, so a brief peak can fall between.
How warm or cold will it be in Hyannis?
At the six-hourly times, the middle forecast runs from 58°F (Sun 8 a.m.) to 67°F (Fri 2 p.m.) EDT. The day’s real high and low can fall between those times.
Are any storms heading for Hyannis?
No storm Stormlines tracks has 1 in 10 forecasts passing its centre within 100 miles of Hyannis this week.

Chance of rain, six hours at a time

Mon 8 p.m.–2 a.m.: 6 in 10 forecasts with measurable rain; middle forecast 0.01 inTue 2–8 a.m.: 1 in 10 forecasts with measurable rain; middle forecast almost noneTue 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneTue 2–8 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneTue 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneWed 2–8 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneWed 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneWed 2–8 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneWed 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 2–8 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 2–8 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneThu 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneFri 2–8 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneFri 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneFri 2–8 p.m.: 2 in 10 forecasts with measurable rain; middle forecast almost noneFri 8 p.m.–2 a.m.: 4 in 10 forecasts with measurable rain; middle forecast almost noneSat 2–8 a.m.: 4 in 10 forecasts with measurable rain; middle forecast almost noneSat 8 a.m.–2 p.m.: 2 in 10 forecasts with measurable rain; middle forecast almost noneSat 2–8 p.m.: 2 in 10 forecasts with measurable rain; middle forecast almost noneSat 8 p.m.–2 a.m.: 1 in 10 forecasts with measurable rain; middle forecast almost noneSun 2–8 a.m.: 3 in 10 forecasts with measurable rain; middle forecast almost noneSun 8 a.m.–2 p.m.: 5 in 10 forecasts with measurable rain; middle forecast almost noneSun 2–8 p.m.: 6 in 10 forecasts with measurable rain; middle forecast 0.11 inSun 8 p.m.–2 a.m.: 6 in 10 forecasts with measurable rain; middle forecast 0.04 inMon 2–8 a.m.: 5 in 10 forecasts with measurable rain; middle forecast almost noneMon 8 a.m.–2 p.m.: 4 in 10 forecasts with measurable rain; middle forecast almost none

Each bar is the share of the 31 forecasts with measurable rain or melted snow in that six hours; the darker the bar, the more forecasts agree. Local days, EDT.

The week, day by day

DayChance of rainA tenth of an inch or moreTotal by day’s endStrongest gustTemperature
Mon 28 (rest of day)6 in 10<1 in 100.01 in · <1 in 1010 mph63°F
Tue 291 in 10<1 in 100.02 in · <1 in 1017 mph59°F–62°F
Wed 30<1 in 10<1 in 100.02 in · <1 in 1010 mph60°F–63°F
Thu 1<1 in 10<1 in 100.02 in · <1 in 1024 mph62°F–66°F
Fri 24 in 10<1 in 100.03 in · <1 in 1026 mph64°F–67°F
Sat 34 in 101 in 100.07 in · <1 in 1024 mph58°F–64°F
Sun 46 in 105 in 100.41 in · 4 in 1023 mph58°F–60°F
Mon 5 (part)5 in 104 in 100.55 in · 5 in 1024 mph · 2 in 10 >40 mph61°F–62°F

Chances are the highest in any six hours of the day. “Total by day’s end” is the middle forecast’s running total since Mon 8 p.m., and the share of forecasts with 0.5 in or more by then; totals aren’t added up day by day, because the middle forecast of each day isn’t the same forecast. Gusts and temperatures are read every six hours.

Storms near Hyannis

No storm Stormlines tracks has 1 in 10 forecasts passing its centre near Hyannis this week. Every storm we’re tracking →

About these numbers

They come from one source, NOAA’s Global Ensemble Forecast System (GEFS): 31 runs of the same model, each started slightly differently, read at Hyannis’s coordinates on a grid about 55 km (35 miles) apart. “8 in 10 forecasts” means 8 in 10 of those runs. Nothing is adjusted for local effects such as coasts, lakes, hills or city heat, so the numbers can differ from your local official forecast, especially for snow and showers.

“Measurable rain” counts rain or melted snow in a six-hour period. Not an official forecast: see the National Weather Service forecast for warnings and decisions. How the forecasts are read: how to read the maps and the glossary.

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