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

This week’s weatherOttawa, ON

Rain is likely in Ottawa on Thursday

8 in 10 of NOAA’s 31 GEFS forecasts bring measurable rain to Ottawa Thu 8 a.m.–2 p.m. EDT; 3 in 10 bring a tenth of an inch or more Thu 2–8 a.m.

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

See it on the globe For warnings, follow your national weather service.

Quick answers

Will it rain in Ottawa this week?
The best chances of measurable rain: Thursday (8 in 10 forecasts, 8 a.m.–2 p.m.); Friday (6 in 10 forecasts, 8 a.m.–2 p.m.); Sunday, Oct. 4 (6 in 10 forecasts, 2–8 p.m.); Monday, Oct. 5 (3 in 10 forecasts, 8 a.m.–2 p.m.). Drier: Tue, Wed, Sat (fewer than 2 in 10 forecasts in any six hours). Times are EDT.
How much rain will Ottawa get this week?
By Mon., Oct. 5, 2 p.m. EDT (the end of the forecast), the middle forecast has 0.66 in of rain and melted snow, counting from Mon 8 p.m. 7 in 10 forecasts bring 0.5 in or more in total; 3 in 10 forecasts bring 1 in or more.
How windy will it get in Ottawa?
Gusts over 30 mph: 1 in 10 forecasts at Mon., Oct. 5, 2 a.m. EDT. The middle forecast’s strongest gust is 25 mph, Sun., Oct. 4, 8 p.m. Checked every six hours, so a brief peak can fall between.
How warm or cold will it be in Ottawa?
At the six-hourly times, the middle forecast runs from 42°F (Sun 2 a.m.) to 71°F (Wed 2 p.m.) EDT. The day’s real high and low can fall between those times.
Are any storms heading for Ottawa?
No storm Stormlines tracks has 1 in 10 forecasts passing its centre within 100 miles of Ottawa this week.

Chance of rain, six hours at a time

Mon 8 p.m.–2 a.m.: 2 in 10 forecasts with measurable rain; middle forecast almost noneTue 2–8 a.m.: fewer than 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.: 4 in 10 forecasts with measurable rain; middle forecast almost noneThu 8 a.m.–2 p.m.: 8 in 10 forecasts with measurable rain; middle forecast 0.03 inThu 2–8 p.m.: 6 in 10 forecasts with measurable rain; middle forecast 0.01 inThu 8 p.m.–2 a.m.: 4 in 10 forecasts with measurable rain; middle forecast almost noneFri 2–8 a.m.: 5 in 10 forecasts with measurable rain; middle forecast almost noneFri 8 a.m.–2 p.m.: 6 in 10 forecasts with measurable rain; middle forecast 0.04 inFri 2–8 p.m.: 4 in 10 forecasts with measurable rain; middle forecast almost noneFri 8 p.m.–2 a.m.: 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 2–8 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 8 a.m.–2 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 2–8 p.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSat 8 p.m.–2 a.m.: fewer than 1 in 10 forecasts with measurable rain; middle forecast almost noneSun 2–8 a.m.: 1 in 10 forecasts with measurable rain; middle forecast almost noneSun 8 a.m.–2 p.m.: 4 in 10 forecasts with measurable rain; middle forecast almost noneSun 2–8 p.m.: 6 in 10 forecasts with measurable rain; middle forecast 0.04 inSun 8 p.m.–2 a.m.: 5 in 10 forecasts with measurable rain; middle forecast almost noneMon 2–8 a.m.: 3 in 10 forecasts with measurable rain; middle forecast almost noneMon 8 a.m.–2 p.m.: 3 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)2 in 10<1 in 10almost none · <1 in 1011 mph55°F
Tue 29<1 in 10<1 in 10almost none · <1 in 105 mph51°F–67°F
Wed 30<1 in 10<1 in 10almost none · <1 in 1017 mph51°F–71°F
Thu 18 in 103 in 100.14 in · <1 in 1024 mph60°F–65°F
Fri 26 in 103 in 100.35 in · 3 in 1016 mph53°F–62°F
Sat 3<1 in 10<1 in 100.35 in · 3 in 1013 mph43°F–60°F
Sun 46 in 104 in 100.63 in · 7 in 1025 mph42°F–56°F
Mon 5 (part)3 in 101 in 100.66 in · 7 in 1022 mph45°F–51°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 Ottawa

No storm Stormlines tracks has 1 in 10 forecasts passing its centre near Ottawa 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 Ottawa’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: follow your national weather service for warnings and decisions. How the forecasts are read: how to read the maps and the glossary.

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