Days without "measureable sunshine" (average, rainfall, places, seasons)

[§AB]

Originally Posted by ColdCanadian

^^ Still better than us mate!
(36 days with 1 hour vs. 62 days with 0.0 hours)

62 days, yuck!

Don't have average stats for overcast days here, unfortunately (or fortunately!!!)

[ADGreen]

Originally Posted by ColdCanadian

^^ Still better than us mate!
(36 days with 1 hour vs. 62 days with 0.0 hours)

In 2009 Sydney recorded:

- 21 days with 0 sunshine hours (11 in summer, 3 in autumn, 1 in winter and 6 in spring),
- 40 days with <= 1 sunshine hours (includes above 21 days)
- 52 days with <= 2 sunshine hours

Conversely, there were 161 days (or 44% of all possible days) that had 9 hours of more of sun. This is a little bit meaningless due to varying day length throughout the year but provides a year-on-year benchmark comparison.

Trying to measure "clear" days, ie days with no cloud cover is more difficult as need to know the maximum amount of potential daylight per day of the year.

Because these stats fascinate me, in 2008 Sydney recorded:

- 24 days with 0 sunshine hours
- 45 days with <= 1 sunshine hours (includes above 21 days)
- 56 days with <= 2 sunshine hours
- 160 days with >= 9 sunshine hours

[B1987]

Days with no sunshine in London.

2010 so far: 26 (extremely high value for so early in the year).
2009: 49
2008: 59
2007: 45

Not that bad compared to the stereotype.

[ColdCanadian]

Originally Posted by B1987

Days with no sunshine in London.

2010 so far: 26 (extremely high value for so early in the year).
2009: 49
2008: 59
2007: 45

Not that bad compared to the stereotype.

Looking at 2007-2009, London England's average "days without sun" is probably less than Toronto!

London, Ontario though is actually worse than Toronto.
Jan: 12.4 days
Feb: 8.7 days
Mar: 8.5 days
Apr: 5.4 days
May: 3.6 days
Jun: 1.4 days
Jul: 0.8 days
Aug: 1.9 days
Sep: 3.7 days
Oct: 5.3 days
Nov: 11.3 days
Dec: 14.6 days
Annual: 77.45 days without measureable sunshine

[ColdCanadian]

Originally Posted by §AB

62 days, yuck!

Don't have average stats for overcast days here, unfortunately (or fortunately!!!)

.

Well technically they weren't days of overcast, but days with measureable sun.
Sounds like they were trying to be optimistic, but I was able easily to convert it into "overcast stats."
Days with measureable sun were mostly-meaningless to me before, so I overlooked them.

[ColdCanadian]

If we can conclude days without measureable sun have 0.0 hours of sunshine
I can use the rest of the year's hours of average sun to figure out the % chance of sun when the sun does come out.

Our annual average % chance of sun is 43.8.

Since the bulk of our overcast days are in winter,
I would be writing off too many daylight hours assuming 12 hrs day length.
But for the purposes of my calculations, I'm estimating avg. hours of monthly daylight.

But plugging in avg daylight hours with each month combined with days without sun,
I can get a new, fairly accurate % chance of sun, for sunny days.

"Written-off" hours of daylight:
Jan: 9.7 days x 9 hrs daylight = 87.3 hrs
Feb: 6.8 days x 10.25 hrs daylight = 69.7 hrs
Mar: 6.7 days x 11.75 hrs daylight = 78.7 hrs
Apr: 3.6 days x 13.25 hrs daylight = 47.7 hrs
May: 2.9 days x 14.5 hrs daylight = 42.1 hrs
Jun: 1.7 days x 15.5 hrs daylight = 26.4 hrs
Jul: 1.0 days x 15 hrs daylight = 15 hrs
Aug: 1.4 days x 14 hrs daylight =19.6 hrs
Sep: 2.8 days x 12.75 hrs daylight = 35.7 hrs
Oct: 3.9 days x 11.25 hrs daylight = 43.9 hrs
Nov: 9.6 days x 10 hrs daylight = 96 hrs
Dec: 12.1 days x 8.75 hrs daylight = 105.9 hrs
Annual: 668 hrs

Annual daylight hours: 4383 hrs?
Annual daylight hours, sunny days only: 3715 hrs
Toronto's annual sunshine hours: 2038 hrs

Toronto's % chance of sun, days with sun only: 54.9% (almost-cheerful )

[RWood]

You can probably up that % a bit, as the 4383 should be too high. Refer earlier remarks.

[ColdCanadian]

Originally Posted by RWood

You can probably up that % a bit, as the 4383 should be too high. Refer earlier remarks.

I forgot, any obstructions/terrain along the horizon.
I simply multiplied 365.25 x 12 hrs to get 4383.

[Ethereal]

Highest we get here per month is 3 days without any sunshine (0.0 hours).

Clouds move a lot in here, and the sun would eventually shine for a few minutes even in the most dullest day.

This was a rather dark month in the past year: Sydney, NSW - April 2014 - Daily Weather Observations

[jgtheone]

Originally Posted by Theropod

Highest we get here per month is 3 days without any sunshine (0.0 hours).

Clouds move a lot in here, and the sun would eventually shine for a few minutes even in the most dullest day.

This was a rather dark month in the past year: Sydney, NSW - April 2014 - Daily Weather Observations

Same here:
Melbourne Airport, Vic - April 2014 - Daily Weather Observations

and

Melbourne Airport, Vic - June 2014 - Daily Weather Observations