Daily sunshine hours per season (climate, record, 2013, Chicago)

[Rozenn]

Originally Posted by Rozenn

^^ Same here, they're unusual. We had 2 sunless days last summer. Unlike during the cool season, there's almost always a break in the cloud cover at some point in the day.
Though very cloudy days (say 2 hours or less) are relatively common. We had 8 of them last summer.
The previous summer has 1 sunless day, but 15 below 2 hours. Granted, that was a very cloudy summer.

For Paris-Montsouris, the long-term average is 3 sunless days and 13 below 2 hours in summer. Winter, the cloudiest season, has 32 sunless days and 54 days below 2 hours on average. Though a day with 2 hours in summer would be cloudier because of the much longer days. Still, summer has much less completely overcast days.

[chicagogeorge]

[nei]

here's one for Portland, which is similar to Paris in latitude and annual range. Since American sunshine recording methods are different from the usual international ones, it's not directly comparable to your Paris graphs. So the sunshine difference is probably smaller than the graphs suggest. But the shapes of the graphs are comparable, and Portland has, as you'd expect a greater seasonality in sunshine.

[Rozenn]

Interesting. As you said, more seasonality in Portland with more very sunny days, compared to Paris' almost flat curves above 1 hour, one of the major differences between the oceanic parts of the PNW and those of Europe.


Graph with percentages. Calculated data from monthly values, so it isn't accurate for months around the equinox (so the spring and fall numbers). Still, gives a broad picture. The lack of days in the 90-100% range is due to the sensor's 120 W/m² threshold. Early morning and late evening are counted in the possible sunshine but even if it's clear, during the minutes following sunrise and preceding sunset, solar irradiance is below 120 W/m². Depends on too many parameters to be bothered working around it.

[Ariete]

Here's a breakdown of Turku in 2013,


January: 55 hours total,

0 sunshine hours: 18 days
0.1-4.9: 6
5<: 5

February: 44 hours,

0: 18
0.1-4.9: 5
5<: 5

March: 270 hours,

0: 1
0.1-4.9: 5
5-9.9: 6
10<: 18

April: 194 hours,

0: 7
0.1-4.9: 6
5-9.9: 6
10<: 11

May: 265 hours,

0: 2
0.1-4.9: 4
5-9.9: 13
10<: 12

June: 298 hours,

0: 1
0.1-4.9: 3
5-9.9: 12
10<: 14

July: 336 hours,

0: 1
0.1-4.9: 3
5-9.9: 8
10<: 19

August: 288 hours,

0: 3
0.1-4.9: 1
5-9.9: 11
10<: 16

September: 173 hours,

0: 2
0.1-4.9: 12
5-9.9: 9
10<: 7

October: 127 hours

0: 7
0.1:-4.9: 11
5-9.9: 11
10<: 2

November: 55 hours

0: 9
0.1-4.9: 16
5-9.9: 5

December: 27 hours

0: 21
0.1-4.9: 10
5-9.9: 0


Seasonal total:

Winter,

0: 57
0.1-4.9: 21
5-9.9: 10

Spring,

0: 37
0.1-4.9: 15
5-9.9: 25
10<: 41

Summer,

0: 5
0.1-4.9: 7
5-9.9: 31
10<: 49

Autumn,

0: 18
0.1-4.9: 39
5-9.9: 25
10<: 9

Most sunshine in one day: 18.2 hours on 19 June (96% of possible daylight, 99% of radiation above 75%).

[MeteoMan]

1.5 hours a day in winter to 6 hours a day in summer.

[ksolina]

From 2.2 hours a day in winter to 8.5 hours a day in summer.