Forecast accuracy

[PaulMy]

I've been using the WU API for their 5-day forecast and adding the current day forecast each day to see how accurate the forecasts are:

The 5-day Forecast for London/Middlesex, Ontario, Canada
Made on Sunday for:    Friday - Afternoon showers. Highs 13 to 15C and lows 4 to 6C.
Made on Monday for:    Friday - Showers. Highs 14 to 16C and lows 4 to 6C.
Made on Tuesday for:   Friday - Showers possible. Highs 13 to 15C and lows 4 to 6C.
Made on Thursday for:  Friday - Windy, and mainly cloudy. Highs 14 to 16C and lows 6 to 8C.
Made on Friday for:      Friday - Windy with morning showers. Highs 14 to 16C and lows 5 to 7C.
Actual...      ****   Friday - Mostly cloudy and windy, 53.5 kmh high gust, High 15.9C and Low 10.2C.

Made on Monday for:    Saturday - Mix of sun and clouds. Highs 13 to 15C and lows 4 to 6C.
Made on Tuesday for:   Saturday - Showers early, windy. Highs 10 to 12C and lows 5 to 7C.
Made on Thursday for:  Saturday - Showers early, windy. Highs 10 to 12C and lows 3 to 5C.
Made on Friday for:      Saturday - Windy with a mix of sun and clouds. Highs 14 to 16C and lows 1 to 3C.
Made on Saturday for:  Saturday - Abundant sunshine. Highs 14 to 16C and lows 1 to 3C.
Actual...      ****   Saturday - Sunshine 13.5 hrs.  High wind gust 47.1 kmh and wind run 292.6 km.  High 17.8C and Lw 7.2C.

Made on Tuesday for:   Sunday - Mix of sun and clouds. Highs 17 to 19C and lows 6 to 8C.
Made on Thursday for:  Sunday - Sunshine. Highs 14 to 16C and lows 5 to 7C.
Made on Friday for:      Sunday - Sunshine. Highs 15 to 17C and lows 4 to 6C.
Made on Saturday for:  Sunday - Abundant sunshine. Highs 16 to 18C and lows 4 to 6C.
Made on Sunday for:    Sunday - Abundant sunshine. Highs 17 to 19C and lows 4 to 6C.
Actual...      *****  Sunday - Sunshine 13.2 hrs. High 18.4C and Low 4.5C.

Made on Thursday for:  Monday - Mostly sunny. Highs 17 to 19C and lows 8 to 10C.
Made on Friday for:      Monday - Mostly sunny. Highs 17 to 19C and lows 7 to 9C.
Made on Saturday for:  Monday - Times of sun and clouds. Highs 18 to 20C and lows 7 to 9C.
Made on Sunday for:    Monday - More sun than clouds. Highs 18 to 20C and lows 6 to 8C.
Made on Monday for:    Monday - Times of sun and clouds. Highs 19 to 21C and lows 6 to 8C.
Actual...      ****   Monday - Sunshine 14.1 hrs.  High 20.9C and Low 4.8C.

Made on Thursday for:  Tuesday - Mostly sunny. Highs 20 to 22C and lows 9 to 11C.
Made on Friday for:      Tuesday - A few clouds. Highs 20 to 22C and lows 9 to 11C.
Made on Saturday for:  Tuesday - Mix of sun and clouds. Highs 21 to 23C and lows 9 to 11C.
Made on Sunday for:    Tuesday - Mix of sun and clouds. Highs 21 to 23C and lows 10 to 12C.
Made on Monday for:    Tuesday - Times of sun and clouds. Highs 21 to 23C and lows 8 to 10C.
Made on Tuesday for:   Tuesday - Mix of sun and clouds. Highs 22 to 24C and lows 10 to 12C.
Actual...      *****  Tuesday - Sunshine 10.6 hrs.  High 24.7C and Low 10.6C.

Made on Friday for:      Wednesday - Partly cloudy. Highs 23 to 25C and lows 11 to 13C.
Made on Saturday for:  Wednesday - More clouds than sun. Highs 23 to 25C and lows 11 to 13C.
Made on Sunday for:    Wednesday - Times of sun and clouds. Highs 24 to 26C and lows 11 to 13C.
Made on Monday for:    Wednesday - Partly cloudy. Highs 23 to 25C and lows 11 to 13C.
Made on Tuesday for:   Wednesday - Times of sun and clouds. Highs 24 to 26C and lows 10 to 12C.
Made on Wednesday for: Wednesday - Partly cloudy. Highs 26 to 28C and lows 10 to 12C.
Actual...      *****  Wednesday - Mostly sunny.  High 26.1C and Low 9.9C.

Made on Saturday for:  Thursday - Plenty of sun. Highs 26 to 28C and lows 14 to 16C.
Made on Sunday for:    Thursday - Times of sun and clouds. Highs 25 to 27C and lows 14 to 16C.
Made on Monday for:    Thursday - Mostly sunny. Highs 26 to 28C and lows 12 to 14C.
Made on Tuesday for:   Thursday - More sun than clouds. Highs 26 to 28C and lows 12 to 14C.
Made on Wednesday for: Thursday - Mix of sun and clouds. Highs 26 to 28C and lows 12 to 14C.
Made on Thursday for:  Thursday - Morning clouds followed by afternoon sun. Highs 27 to 29C and lows 13 to 15C.
Actual...      ****   Thursday - Mostly sunny and hot, 12.1 hrs sunshine, High 28.3C and Low 8.7C.

Made on Sunday for:    Friday - Mix of sun and clouds. Highs 26 to 28C and lows 15 to 17C.
Made on Monday for:    Friday - More sun than clouds. Highs 24 to 26C and lows 14 to 16C.
Made on Tuesday for:   Friday - More sun than clouds. Highs 25 to 27C and lows 13 to 15C.
Made on Wednesday for: Friday - Plenty of sun. Highs 25 to 27C and lows 13 to 15C.
Made on Thursday for:  Friday - Mix of sun and clouds. Highs 26 to 28C and lows 14 to 16C.
Made on Friday for:    Friday - Partly cloudy. Highs 26 to 28C and lows 14 to 16C.

During our current hot streak with plenty of sunshine, the forecasts have been pretty close.  In previous periods when rain (or snow) was in the forecast there was much more disparity.

Enjoy,
Paul

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