Paris
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Paris clear sky chart from 2005-11-06 to 2024-08-30.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	13% 6% 2 5% 4 4 4 3 5% 7% 47%	95602
	Night	12% 5% 2 5% 3 3 3 3 5% 6% 52%	93508
Transparency	Day	37% 5% 10% 23% 20% 5%	95378
	Night	33% 5% 10% 22% 23% 8%	93338
Seeing	Day	14% 6% 21% 28% 23% 8%	15039
	Night	14% 6% 26% 34% 18% 2	24825

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	15% 8% 3 5% 4 3 3 3 4 5% 50%	2847
	11th to 20th	Day	12% 5% 1 4 2 2 2 2 4 5% 61%	2850
	21st to end	Day	21% 7% 3 6% 3 3 3 2 3 4 45%	3135
February	1st to 10th	Day	20% 9% 3 6% 4 3 3 3 3 6% 40%	1710
	11th to 20th	Day	20% 6% 2 6% 4 3 4 3 4 5% 44%	1834
	21st to end	Day	24% 7% 2 4 2 3 3 2 3 4 46%	1668
March	1st to 10th	Day	17% 7% 2 5% 3 3 3 3 4 6% 46%	3436
	11th to 20th	Day	17% 7% 3 6% 4 4 4 4 5% 6% 40%	3480
	21st to end	Day	18% 9% 3 6% 5% 4 4 3 4 6% 39%	3814
April	1st to 10th	Day	15% 6% 3 6% 5% 3 3 3 5% 6% 46%	2090
	11th to 20th	Day	16% 6% 2 5% 4 4 4 4 4 7% 44%	2254
	21st to end	Day	16% 6% 2 5% 5% 4 4 3 5% 7% 44%	2312
May	1st to 10th	Day	20% 7% 2 7% 4 4 4 3 5% 6% 38%	4082
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 6% 46%	4082
	21st to end	Day	18% 8% 3 7% 5% 4 5% 3 5% 7% 34%	4477
June	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 8% 44%	2470
	11th to 20th	Day	6% 4 3 5% 5% 5% 5% 5% 7% 7% 47%	2470
	21st to end	Day	5% 3 1 4 4 4 5% 4 7% 10% 52%	2470
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 10% 44%	4120
	11th to 20th	Day	3 3 1 4 3 4 4 4 7% 9% 57%	4120
	21st to end	Day	7% 6% 3 7% 6% 5% 6% 5% 7% 9% 38%	4465
August	1st to 10th	Day	3 2 1 3 4 4 4 5% 7% 9% 56%	2458
	11th to 20th	Day	8% 4 2 5% 5% 4 4 3 6% 9% 49%	2431
	21st to end	Day	6% 4 2 4 4 4 6% 5% 6% 10% 47%	2489
September	1st to 10th	Day	9% 4 3 6% 4 4 4 3 5% 6% 51%	2015
	11th to 20th	Day	11% 5% 2 5% 4 4 6% 4 5% 7% 47%	1980
	21st to end	Day	8% 4 2 4 3 4 4 3 5% 6% 57%	1980
October	1st to 10th	Day	7% 4 2 5% 4 3 4 2 4 6% 58%	1856
	11th to 20th	Day	15% 5% 2 3 2 2 3 2 4 4 58%	1800
	21st to end	Day	17% 6% 2 4 2 3 3 3 3 4 54%	1980
November	1st to 10th	Day	13% 5% 1 5% 3 3 3 3 4 5% 54%	1858
	11th to 20th	Day	10% 5% 2 4 4 3 3 3 4 6% 57%	1853
	21st to end	Day	17% 7% 2 4 3 2 3 2 3 5% 53%	1710
December	1st to 10th	Day	17% 6% 2 5% 3 4 3 3 3 5% 50%	1710
	11th to 20th	Day	15% 10% 3 6% 4 3 3 3 4 5% 44%	2161
	21st to end	Day	19% 8% 2 5% 3 3 3 3 4 5% 45%	3135
January	1st to 10th	Night	14% 8% 2 5% 2 3 3 2 5% 5% 52%	4108
	11th to 20th	Night	12% 6% 1 3 2 2 2 2 3 5% 60%	4120
	21st to end	Night	23% 6% 2 5% 3 3 2 2 3 4 46%	4532
February	1st to 10th	Night	17% 7% 2 5% 4 4 3 3 4 4 48%	2470
	11th to 20th	Night	18% 7% 2 5% 3 3 4 2 4 4 47%	2247
	21st to end	Night	18% 7% 2 5% 3 3 2 2 4 5% 50%	1784
March	1st to 10th	Night	17% 8% 3 7% 4 4 3 3 5% 5% 41%	3419
	11th to 20th	Night	16% 6% 2 5% 4 4 3 3 4 5% 47%	3480
	21st to end	Night	16% 6% 3 5% 4 3 4 3 5% 6% 46%	3817
April	1st to 10th	Night	12% 5% 2 5% 3 4 3 3 5% 6% 51%	2090
	11th to 20th	Night	14% 5% 2 4 3 3 4 3 6% 7% 49%	1875
	21st to end	Night	12% 6% 2 5% 3 3 4 2 4 7% 51%	1864
May	1st to 10th	Night	18% 8% 3 6% 4 4 4 3 6% 7% 38%	2823
	11th to 20th	Night	14% 4 2 5% 3 3 4 3 6% 8% 49%	2823
	21st to end	Night	12% 6% 2 6% 4 4 5% 5% 6% 9% 41%	3090
June	1st to 10th	Night	5% 4 2 4 4 4 4 3 6% 9% 56%	1710
	11th to 20th	Night	4 4 1 3 3 3 3 4 5% 10% 60%	1710
	21st to end	Night	4 2 1 4 3 2 3 4 7% 9% 62%	1710
July	1st to 10th	Night	6% 3 1 4 4 4 4 4 6% 11% 53%	2850
	11th to 20th	Night	4 3 1 3 2 3 2 3 5% 9% 65%	2850
	21st to end	Night	5% 3 2 6% 5% 4 6% 5% 6% 9% 49%	3098
August	1st to 10th	Night	3 2 1 3 2 2 4 3 6% 12% 62%	1701
	11th to 20th	Night	5% 3 1 4 3 4 4 3 6% 11% 56%	1690
	21st to end	Night	3 3 1 5% 4 4 5% 5% 6% 9% 53%	2075
September	1st to 10th	Night	6% 4 1 5% 3 3 4 3 5% 7% 59%	1940
	11th to 20th	Night	10% 4 2 5% 4 4 3 4 6% 7% 51%	1980
	21st to end	Night	7% 3 1 4 3 2 3 2 5% 7% 64%	1980
October	1st to 10th	Night	7% 3 1 3 2 3 3 3 5% 7% 61%	2084
	11th to 20th	Night	13% 5% 1 4 2 3 2 2 4 4 62%	2160
	21st to end	Night	16% 6% 1 4 2 2 2 2 2 4 59%	2376
November	1st to 10th	Night	11% 4 1 5% 3 3 3 3 4 5% 59%	2220
	11th to 20th	Night	9% 5% 1 4 3 3 3 3 4 5% 58%	2324
	21st to end	Night	17% 7% 2 4 2 3 3 3 4 5% 51%	2470
December	1st to 10th	Night	15% 6% 2 3 4 3 3 3 4 6% 52%	2470
	11th to 20th	Night	14% 7% 3 5% 4 4 3 2 4 4 49%	3036
	21st to end	Night	17% 7% 2 4 3 3 3 3 4 6% 49%	4532

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	38% 4 6% 23% 25% 4	2848
	11th to 20th	Day	28% 2 10% 28% 27% 5%	2850
	21st to end	Day	46% 3 4 17% 22% 8%	3135
February	1st to 10th	Day	47% 4 7% 17% 19% 6%	1710
	11th to 20th	Day	43% 4 6% 20% 19% 7%	1844
	21st to end	Day	44% 3 4 15% 24% 9%	1668
March	1st to 10th	Day	40% 5% 6% 16% 24% 9%	3436
	11th to 20th	Day	44% 5% 9% 20% 18% 4	3480
	21st to end	Day	46% 5% 8% 21% 18% 3	3814
April	1st to 10th	Day	40% 4 8% 22% 18% 8%	2090
	11th to 20th	Day	40% 4 9% 20% 19% 7%	2254
	21st to end	Day	40% 5% 8% 21% 22% 4	2312
May	1st to 10th	Day	46% 6% 9% 23% 13% 3	4120
	11th to 20th	Day	37% 6% 11% 24% 20% 1	4086
	21st to end	Day	49% 7% 11% 18% 13% 3	4489
June	1st to 10th	Day	34% 7% 13% 27% 16% 3	2470
	11th to 20th	Day	32% 7% 14% 26% 18% 3	2470
	21st to end	Day	25% 7% 13% 31% 21% 3	2470
July	1st to 10th	Day	33% 7% 19% 30% 11% 1	4056
	11th to 20th	Day	21% 6% 11% 38% 22% 2	4051
	21st to end	Day	37% 8% 15% 29% 11%	4325
August	1st to 10th	Day	22% 6% 15% 33% 21% 3	2444
	11th to 20th	Day	31% 6% 15% 28% 17% 3	2431
	21st to end	Day	30% 8% 16% 29% 14% 3	2489
September	1st to 10th	Day	34% 5% 9% 23% 21% 8%	2015
	11th to 20th	Day	34% 7% 11% 20% 20% 8%	1980
	21st to end	Day	26% 5% 9% 22% 26% 12%	1980
October	1st to 10th	Day	28% 4 11% 21% 22% 14%	1856
	11th to 20th	Day	31% 3 6% 16% 29% 16%	1800
	21st to end	Day	35% 3 7% 17% 26% 12%	1980
November	1st to 10th	Day	33% 4 8% 24% 23% 8%	1858
	11th to 20th	Day	30% 3 8% 22% 29% 9%	1853
	21st to end	Day	36% 3 6% 18% 29% 8%	1710
December	1st to 10th	Day	38% 4 8% 24% 21% 6%	1710
	11th to 20th	Day	43% 3 5% 18% 23% 8%	2159
	21st to end	Day	41% 4 5% 20% 24% 6%	3135
January	1st to 10th	Night	35% 4 6% 19% 31% 6%	4108
	11th to 20th	Night	30% 3 10% 22% 27% 8%	4120
	21st to end	Night	44% 3 6% 16% 23% 9%	4532
February	1st to 10th	Night	40% 3 7% 20% 21% 9%	2470
	11th to 20th	Night	42% 2 7% 19% 22% 8%	2247
	21st to end	Night	39% 3 6% 17% 22% 13%	1784
March	1st to 10th	Night	45% 4 7% 15% 17% 12%	3419
	11th to 20th	Night	39% 5% 8% 22% 17% 10%	3480
	21st to end	Night	39% 5% 9% 19% 25% 3	3817
April	1st to 10th	Night	34% 4 10% 20% 19% 13%	2090
	11th to 20th	Night	35% 4 8% 21% 20% 12%	1875
	21st to end	Night	32% 4 11% 23% 24% 5%	1864
May	1st to 10th	Night	44% 7% 10% 20% 13% 6%	2850
	11th to 20th	Night	33% 6% 15% 25% 20% 2	2824
	21st to end	Night	37% 8% 15% 22% 12% 6%	3099
June	1st to 10th	Night	24% 7% 13% 31% 21% 3	1710
	11th to 20th	Night	20% 5% 12% 34% 23% 6%	1710
	21st to end	Night	19% 7% 12% 30% 28% 5%	1710
July	1st to 10th	Night	25% 6% 19% 32% 16% 2	2805
	11th to 20th	Night	16% 5% 11% 39% 26% 3	2796
	21st to end	Night	29% 7% 16% 30% 17% 1	2999
August	1st to 10th	Night	15% 5% 16% 33% 26% 5%	1691
	11th to 20th	Night	23% 6% 12% 32% 22% 5%	1690
	21st to end	Night	26% 6% 15% 31% 20% 3	2075
September	1st to 10th	Night	25% 5% 11% 23% 27% 9%	1940
	11th to 20th	Night	31% 5% 11% 21% 21% 11%	1980
	21st to end	Night	22% 4 9% 22% 28% 16%	1980
October	1st to 10th	Night	22% 4 11% 24% 21% 17%	2084
	11th to 20th	Night	27% 4 6% 16% 27% 20%	2160
	21st to end	Night	32% 3 4 20% 26% 15%	2376
November	1st to 10th	Night	29% 4 8% 20% 26% 13%	2220
	11th to 20th	Night	28% 3 8% 21% 27% 13%	2324
	21st to end	Night	36% 3 7% 18% 28% 8%	2470
December	1st to 10th	Night	34% 3 10% 20% 23% 10%	2470
	11th to 20th	Night	40% 3 5% 16% 25% 11%	3037
	21st to end	Night	37% 4 6% 21% 25% 7%	4532

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	22% 11% 34% 27% 6%	270
	11th to 20th	Day	20% 17% 35% 21% 4 2	270
	21st to end	Day	20% 12% 38% 21% 8% 1	297
February	1st to 10th	Day	26% 11% 35% 21% 7% 1	270
	11th to 20th	Day	24% 16% 39% 17% 3	270
	21st to end	Day	34% 12% 39% 12% 3	225
March	1st to 10th	Day	21% 12% 39% 22% 6%	270
	11th to 20th	Day	26% 16% 34% 17% 6% 2	270
	21st to end	Day	21% 15% 39% 22% 3	297
April	1st to 10th	Day	23% 14% 34% 22% 6%	270
	11th to 20th	Day	25% 12% 30% 24% 8%	452
	21st to end	Day	20% 9% 36% 25% 9% 2	492
May	1st to 10th	Day	17% 9% 32% 32% 9% 1	653
	11th to 20th	Day	16% 4 27% 34% 15% 3	675
	21st to end	Day	15% 7% 23% 33% 17% 6%	734
June	1st to 10th	Day	10% 3 10% 37% 30% 10%	680
	11th to 20th	Day	7% 1 14% 40% 30% 8%	680
	21st to end	Day	7% 2 11% 32% 35% 13%	680
July	1st to 10th	Day	9% 2 8% 31% 35% 16%	671
	11th to 20th	Day	2 8% 31% 43% 15%	668
	21st to end	Day	4 2 5% 31% 41% 17%	739
August	1st to 10th	Day	5% 5% 33% 44% 14%	676
	11th to 20th	Day	8% 1 6% 32% 41% 11%	665
	21st to end	Day	7% 1 3 22% 40% 26%	536
September	1st to 10th	Day	7% 2 4 20% 42% 26%	305
	11th to 20th	Day	5% 10% 23% 38% 23%	270
	21st to end	Day	11% 3 9% 29% 29% 19%	270
October	1st to 10th	Day	5% 3 19% 32% 33% 9%	270
	11th to 20th	Day	15% 5% 28% 29% 19% 4	270
	21st to end	Day	27% 7% 25% 22% 17% 1	297
November	1st to 10th	Day	19% 4 31% 28% 13% 5%	270
	11th to 20th	Day	15% 7% 37% 29% 10% 3	270
	21st to end	Day	21% 12% 30% 25% 9% 3	270
December	1st to 10th	Day	22% 11% 30% 25% 11% 1	270
	11th to 20th	Day	24% 9% 38% 23% 5% 1	270
	21st to end	Day	19% 13% 41% 21% 5% 1	297
January	1st to 10th	Night	18% 10% 33% 31% 7%	950
	11th to 20th	Night	20% 12% 35% 26% 7%	950
	21st to end	Night	17% 8% 38% 30% 6%	1045
February	1st to 10th	Night	22% 11% 33% 28% 5%	950
	11th to 20th	Night	23% 10% 37% 27% 3	773
	21st to end	Night	23% 13% 39% 22% 3	528
March	1st to 10th	Night	20% 9% 36% 29% 6%	570
	11th to 20th	Night	18% 9% 37% 31% 5%	570
	21st to end	Night	15% 10% 39% 30% 5% 1	627
April	1st to 10th	Night	13% 11% 43% 27% 7%	570
	11th to 20th	Night	16% 10% 39% 26% 9%	563
	21st to end	Night	15% 7% 39% 29% 9% 1	570
May	1st to 10th	Night	12% 7% 36% 36% 9% 1	570
	11th to 20th	Night	13% 3 29% 37% 16% 1	561
	21st to end	Night	9% 4 24% 38% 22% 3	617
June	1st to 10th	Night	6% 3 12% 43% 34% 3	570
	11th to 20th	Night	6% 1 18% 50% 24% 1	570
	21st to end	Night	4 1 11% 39% 40% 5%	570
July	1st to 10th	Night	4 1 8% 40% 43% 5%	555
	11th to 20th	Night	4 1 6% 35% 47% 6%	552
	21st to end	Night	3 2 6% 36% 45% 7%	624
August	1st to 10th	Night	4 1 5% 42% 43% 6%	567
	11th to 20th	Night	7% 1 5% 40% 42% 5%	564
	21st to end	Night	5% 1 2 40% 44% 7%	624
September	1st to 10th	Night	7% 1 6% 34% 45% 6%	540
	11th to 20th	Night	13% 1 6% 36% 40% 4	540
	21st to end	Night	8% 1 11% 42% 34% 4	540
October	1st to 10th	Night	9% 1 15% 43% 29% 3	644
	11th to 20th	Night	14% 4 24% 38% 17% 2	720
	21st to end	Night	20% 5% 29% 29% 15% 2	792
November	1st to 10th	Night	12% 3 29% 39% 15% 1	740
	11th to 20th	Night	12% 8% 30% 39% 10% 1	804
	21st to end	Night	21% 8% 31% 29% 11%	950
December	1st to 10th	Night	18% 8% 33% 34% 7%	950
	11th to 20th	Night	22% 8% 32% 32% 6%	950
	21st to end	Night	20% 10% 33% 30% 8%	1045

Page generated at 2024-08-27 08:49:39. Version ac07

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