Berne
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Berne clear sky chart from 2005-11-06 to 2025-02-06.

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	14% 10% 4 8% 5% 5% 4 4 5% 7% 34%	108406
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	109954
Transparency	Day	47% 5% 12% 21% 13% 1	112049
	Night	48% 5% 11% 21% 13% 2	114439
Seeing	Day	17% 10% 26% 24% 16% 7%	15863
	Night	19% 9% 28% 29% 14% 1	25800

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	12% 17% 10% 18% 6% 5% 4 3 3 4 19%	3617
	11th to 20th	Day	13% 16% 9% 13% 7% 7% 7% 5% 4 4 17%	3620
	21st to end	Day	23% 17% 9% 11% 5% 3 3 3 3 4 19%	4315
February	1st to 10th	Day	17% 16% 6% 12% 6% 5% 4 3 5% 6% 21%	1843
	11th to 20th	Day	15% 12% 4 14% 8% 5% 5% 3 4 6% 25%	1848
	21st to end	Day	15% 15% 5% 11% 4 4 3 3 4 6% 28%	1570
March	1st to 10th	Day	20% 20% 5% 8% 5% 3 3 2 4 5% 24%	3120
	11th to 20th	Day	13% 9% 3 7% 5% 4 4 3 6% 7% 37%	3448
	21st to end	Day	19% 10% 5% 11% 5% 5% 4 4 5% 7% 26%	3842
April	1st to 10th	Day	14% 12% 4 9% 6% 5% 4 4 6% 6% 30%	2280
	11th to 20th	Day	17% 9% 2 8% 4 5% 3 3 5% 7% 36%	2304
	21st to end	Day	19% 7% 3 7% 4 5% 5% 3 6% 8% 32%	2470
May	1st to 10th	Day	19% 10% 3 7% 5% 5% 6% 4 6% 7% 28%	4082
	11th to 20th	Day	18% 7% 2 6% 4 5% 5% 3 6% 8% 37%	4081
	21st to end	Day	9% 5% 2 7% 5% 5% 5% 5% 7% 10% 39%	4476
June	1st to 10th	Day	11% 5% 2 7% 5% 4 6% 4 6% 8% 41%	2657
	11th to 20th	Day	10% 5% 3 5% 4 5% 5% 5% 7% 9% 42%	2660
	21st to end	Day	11% 5% 2 6% 6% 6% 6% 4 7% 10% 38%	2660
July	1st to 10th	Day	12% 7% 2 7% 5% 5% 5% 5% 7% 10% 36%	4440
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 5% 7% 11% 46%	4440
	21st to end	Day	7% 6% 3 8% 5% 5% 6% 5% 7% 9% 38%	4573
August	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 4 8% 11% 43%	4104
	11th to 20th	Day	8% 6% 2 6% 4 4 5% 5% 7% 9% 44%	4044
	21st to end	Day	7% 4 2 6% 4 4 4 4 6% 10% 49%	4214
September	1st to 10th	Day	11% 6% 2 5% 5% 3 4 4 5% 7% 48%	2199
	11th to 20th	Day	9% 5% 3 6% 4 4 5% 3 6% 8% 48%	2090
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 7% 43%	2090
October	1st to 10th	Day	11% 6% 2 7% 5% 4 4 4 5% 6% 45%	2090
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 4 5% 7% 42%	1933
	21st to end	Day	18% 10% 3 8% 6% 5% 5% 3 5% 7% 30%	1881
November	1st to 10th	Day	10% 7% 2 6% 5% 3 4 3 5% 6% 49%	1762
	11th to 20th	Day	16% 13% 4 8% 4 5% 4 3 5% 6% 32%	1800
	21st to end	Day	19% 13% 4 10% 5% 5% 4 2 4 5% 29%	1800
December	1st to 10th	Day	12% 15% 5% 10% 5% 4 5% 3 4 6% 31%	2930
	11th to 20th	Day	16% 18% 6% 12% 5% 4 4 4 4 5% 22%	3141
	21st to end	Day	25% 19% 8% 12% 6% 5% 4 3 4 5% 12%	3982
January	1st to 10th	Night	15% 16% 8% 15% 6% 5% 4 3 4 5% 21%	6348
	11th to 20th	Night	12% 19% 9% 15% 8% 6% 5% 4 4 3 16%	6360
	21st to end	Night	21% 13% 6% 9% 5% 5% 5% 4 4 4 26%	6632
February	1st to 10th	Night	19% 15% 6% 9% 6% 5% 4 3 4 5% 25%	2446
	11th to 20th	Night	12% 13% 4 10% 8% 4 4 4 5% 5% 30%	2218
	21st to end	Night	20% 12% 5% 9% 5% 4 4 3 4 5% 28%	1884
March	1st to 10th	Night	18% 15% 4 7% 4 3 3 3 3 5% 34%	3733
	11th to 20th	Night	11% 7% 2 5% 4 4 4 4 5% 8% 45%	3512
	21st to end	Night	18% 9% 3 8% 5% 4 4 3 5% 6% 36%	3817
April	1st to 10th	Night	15% 9% 3 6% 5% 3 5% 4 6% 7% 36%	1900
	11th to 20th	Night	17% 9% 2 6% 5% 4 5% 4 5% 7% 36%	1825
	21st to end	Night	17% 10% 3 5% 4 4 4 3 6% 6% 37%	1710
May	1st to 10th	Night	17% 9% 4 8% 5% 5% 5% 4 6% 7% 30%	2813
	11th to 20th	Night	20% 7% 2 6% 3 4 4 3 5% 8% 38%	2812
	21st to end	Night	10% 5% 2 5% 4 4 6% 4 7% 9% 44%	3065
June	1st to 10th	Night	9% 4 2 6% 5% 4 4 4 6% 9% 48%	1520
	11th to 20th	Night	8% 6% 2 5% 4 4 5% 4 7% 7% 48%	1520
	21st to end	Night	8% 6% 2 6% 5% 4 4 4 7% 9% 45%	1520
July	1st to 10th	Night	10% 5% 1 6% 4 4 4 4 6% 9% 47%	2530
	11th to 20th	Night	6% 4 2 4 3 3 4 3 6% 9% 54%	2530
	21st to end	Night	9% 6% 3 7% 4 4 4 3 6% 10% 43%	2982
August	1st to 10th	Night	12% 5% 2 6% 5% 4 5% 3 6% 9% 43%	2825
	11th to 20th	Night	7% 6% 3 6% 4 4 5% 4 6% 8% 49%	2785
	21st to end	Night	6% 4 2 6% 4 5% 5% 4 6% 8% 50%	3438
September	1st to 10th	Night	12% 6% 1 5% 3 3 4 3 5% 7% 52%	1962
	11th to 20th	Night	9% 5% 2 4 3 3 3 3 6% 7% 55%	2090
	21st to end	Night	12% 7% 2 5% 4 4 4 3 5% 5% 49%	2090
October	1st to 10th	Night	11% 5% 2 5% 3 3 4 3 6% 6% 52%	2090
	11th to 20th	Night	17% 8% 2 5% 4 4 3 3 5% 6% 42%	2241
	21st to end	Night	19% 7% 2 6% 5% 4 4 4 5% 7% 37%	2717
November	1st to 10th	Night	12% 8% 3 5% 4 4 3 4 5% 6% 46%	2536
	11th to 20th	Night	15% 11% 4 8% 5% 4 3 3 5% 7% 35%	2600
	21st to end	Night	18% 14% 4 10% 6% 4 4 3 4 6% 28%	2600
December	1st to 10th	Night	13% 12% 4 9% 5% 5% 6% 4 7% 7% 29%	4250
	11th to 20th	Night	17% 17% 9% 12% 4 4 4 3 4 4 21%	5057
	21st to end	Night	26% 19% 7% 10% 6% 4 4 3 4 4 13%	6996

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	70% 4 7% 15% 4	3618
	11th to 20th	Day	72% 3 9% 7% 7% 2	3620
	21st to end	Day	71% 2 8% 11% 7%	4315
February	1st to 10th	Day	65% 3 10% 13% 7% 1	1843
	11th to 20th	Day	60% 4 9% 19% 7% 1	1858
	21st to end	Day	59% 3 12% 17% 6% 2	1570
March	1st to 10th	Day	63% 4 7% 18% 7%	3120
	11th to 20th	Day	45% 4 10% 31% 10% 1	3448
	21st to end	Day	57% 5% 17% 17% 4	3842
April	1st to 10th	Day	53% 5% 12% 19% 11% 1	2280
	11th to 20th	Day	48% 5% 10% 22% 12% 3	2304
	21st to end	Day	49% 5% 13% 20% 11% 3	2470
May	1st to 10th	Day	53% 7% 12% 20% 9%	4120
	11th to 20th	Day	45% 6% 13% 26% 10% 1	4085
	21st to end	Day	36% 9% 12% 22% 19% 2	4489
June	1st to 10th	Day	39% 6% 11% 26% 15% 2	2657
	11th to 20th	Day	36% 6% 13% 25% 17% 2	2660
	21st to end	Day	39% 7% 15% 20% 14% 4	2660
July	1st to 10th	Day	43% 5% 12% 21% 16% 2	4371
	11th to 20th	Day	30% 6% 15% 28% 20% 2	4365
	21st to end	Day	39% 7% 15% 18% 17% 4	4428
August	1st to 10th	Day	33% 6% 19% 26% 15% 1	4091
	11th to 20th	Day	34% 6% 14% 31% 16% 1	4083
	21st to end	Day	31% 6% 14% 30% 16% 3	4213
September	1st to 10th	Day	36% 5% 13% 23% 19% 4	2199
	11th to 20th	Day	34% 5% 11% 25% 22% 2	2090
	21st to end	Day	41% 5% 10% 23% 20% 1	2090
October	1st to 10th	Day	27% 4 11% 32% 24% 1	3480
	11th to 20th	Day	34% 4 11% 24% 26% 1	3187
	21st to end	Day	43% 3 10% 26% 17% 2	3081
November	1st to 10th	Day	35% 5% 13% 28% 18% 1	1762
	11th to 20th	Day	54% 3 10% 19% 11% 2	1800
	21st to end	Day	59% 3 11% 19% 7% 1	1800
December	1st to 10th	Day	54% 4 15% 21% 6%	2930
	11th to 20th	Day	64% 4 12% 16% 4	3138
	21st to end	Day	76% 3 8% 9% 4	3982
January	1st to 10th	Night	67% 3 8% 15% 7%	6348
	11th to 20th	Night	73% 3 7% 9% 8%	6360
	21st to end	Night	62% 3 11% 15% 7% 1	6632
February	1st to 10th	Night	62% 4 11% 15% 8% 1	2446
	11th to 20th	Night	56% 4 10% 19% 11% 1	2219
	21st to end	Night	58% 4 10% 16% 10% 2	1884
March	1st to 10th	Night	53% 4 9% 24% 10% 1	3733
	11th to 20th	Night	36% 7% 11% 29% 16% 2	3512
	21st to end	Night	49% 5% 12% 26% 7% 1	3817
April	1st to 10th	Night	47% 5% 12% 22% 14% 1	1900
	11th to 20th	Night	46% 4 11% 20% 15% 3	1825
	21st to end	Night	47% 5% 11% 21% 13% 4	1710
May	1st to 10th	Night	52% 6% 11% 21% 9% 2	2840
	11th to 20th	Night	43% 6% 13% 26% 10% 1	2813
	21st to end	Night	33% 9% 15% 23% 17% 3	3073
June	1st to 10th	Night	33% 5% 9% 29% 20% 3	1520
	11th to 20th	Night	33% 6% 13% 26% 19% 3	1520
	21st to end	Night	35% 6% 15% 24% 16% 4	1520
July	1st to 10th	Night	35% 5% 11% 27% 16% 6%	2490
	11th to 20th	Night	25% 5% 15% 29% 23% 2	2482
	21st to end	Night	36% 5% 16% 18% 19% 5%	2887
August	1st to 10th	Night	36% 6% 14% 28% 14% 1	2814
	11th to 20th	Night	32% 6% 13% 30% 18% 1	2812
	21st to end	Night	30% 5% 14% 27% 20% 3	3438
September	1st to 10th	Night	32% 5% 14% 24% 20% 5%	1962
	11th to 20th	Night	28% 5% 9% 28% 28% 3	2090
	21st to end	Night	36% 5% 11% 24% 21% 3	2090
October	1st to 10th	Night	23% 4 8% 30% 34% 2	3480
	11th to 20th	Night	33% 3 11% 24% 28% 1	3714
	21st to end	Night	34% 4 8% 30% 21% 3	4467
November	1st to 10th	Night	39% 4 10% 27% 19% 2	2536
	11th to 20th	Night	49% 3 10% 20% 14% 3	2600
	21st to end	Night	59% 3 10% 20% 7%	2600
December	1st to 10th	Night	52% 5% 14% 24% 6%	4250
	11th to 20th	Night	66% 4 12% 12% 6%	5059
	21st to end	Night	74% 4 10% 9% 3	6996

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	21% 20% 36% 19% 4 1	300
	11th to 20th	Day	23% 18% 41% 13% 5%	300
	21st to end	Day	31% 14% 34% 15% 6%	330
February	1st to 10th	Day	29% 18% 33% 15% 5%	285
	11th to 20th	Day	25% 18% 34% 17% 5% 1	270
	21st to end	Day	28% 18% 40% 13% 1	225
March	1st to 10th	Day	26% 17% 36% 17% 4	270
	11th to 20th	Day	26% 13% 30% 22% 7% 1	441
	21st to end	Day	29% 15% 31% 17% 7%	506
April	1st to 10th	Day	19% 15% 33% 22% 9% 2	460
	11th to 20th	Day	20% 18% 27% 22% 9% 3	452
	21st to end	Day	23% 12% 33% 20% 10% 2	460
May	1st to 10th	Day	23% 13% 29% 23% 8% 4	463
	11th to 20th	Day	22% 7% 26% 23% 16% 7%	487
	21st to end	Day	12% 5% 26% 28% 18% 11%	529
June	1st to 10th	Day	11% 7% 25% 30% 21% 6%	677
	11th to 20th	Day	12% 6% 25% 29% 21% 6%	680
	21st to end	Day	13% 7% 26% 27% 19% 8%	680
July	1st to 10th	Day	11% 4 17% 27% 23% 18%	671
	11th to 20th	Day	7% 3 23% 28% 25% 14%	668
	21st to end	Day	8% 2 16% 34% 28% 13%	600
August	1st to 10th	Day	8% 2 16% 29% 26% 19%	486
	11th to 20th	Day	11% 4 17% 27% 28% 13%	479
	21st to end	Day	9% 2 12% 28% 32% 16%	539
September	1st to 10th	Day	13% 4 14% 26% 29% 13%	490
	11th to 20th	Day	8% 3 14% 25% 31% 19%	490
	21st to end	Day	20% 9% 19% 23% 21% 8%	490
October	1st to 10th	Day	10% 7% 24% 31% 20% 8%	490
	11th to 20th	Day	15% 14% 29% 27% 12% 3	485
	21st to end	Day	27% 14% 35% 20% 5% 1	330
November	1st to 10th	Day	11% 14% 35% 24% 12% 3	300
	11th to 20th	Day	23% 18% 31% 16% 11% 1	300
	21st to end	Day	31% 12% 37% 17% 4	300
December	1st to 10th	Day	21% 18% 37% 17% 6%	300
	11th to 20th	Day	21% 15% 41% 16% 7% 1	300
	21st to end	Day	29% 19% 30% 18% 4	330
January	1st to 10th	Night	22% 17% 35% 22% 5%	1000
	11th to 20th	Night	25% 14% 37% 19% 4 1	1000
	21st to end	Night	23% 15% 35% 23% 4	944
February	1st to 10th	Night	28% 11% 34% 23% 4	781
	11th to 20th	Night	20% 13% 40% 25% 3	743
	21st to end	Night	26% 13% 37% 21% 3	628
March	1st to 10th	Night	21% 14% 33% 26% 7%	760
	11th to 20th	Night	18% 12% 36% 27% 6% 1	760
	21st to end	Night	24% 11% 30% 27% 7%	836
April	1st to 10th	Night	19% 11% 34% 29% 6% 1	570
	11th to 20th	Night	21% 12% 33% 26% 8% 1	563
	21st to end	Night	21% 8% 38% 22% 10% 1	570
May	1st to 10th	Night	20% 9% 32% 32% 7% 1	570
	11th to 20th	Night	24% 4 26% 28% 17% 1	561
	21st to end	Night	11% 2 24% 40% 21% 2	617
June	1st to 10th	Night	10% 2 25% 44% 18% 1	570
	11th to 20th	Night	10% 3 22% 41% 22% 1	570
	21st to end	Night	10% 3 24% 37% 25% 1	570
July	1st to 10th	Night	10% 2 15% 38% 30% 5%	555
	11th to 20th	Night	8% 3 15% 41% 29% 4	552
	21st to end	Night	9% 2 12% 44% 31% 2	624
August	1st to 10th	Night	9% 1 11% 42% 32% 4	567
	11th to 20th	Night	9% 2 13% 42% 31% 4	564
	21st to end	Night	7% 1 12% 36% 38% 5%	627
September	1st to 10th	Night	15% 3 13% 36% 29% 4	632
	11th to 20th	Night	10% 3 12% 36% 35% 4	760
	21st to end	Night	15% 6% 22% 32% 22% 3	760
October	1st to 10th	Night	13% 5% 24% 35% 18% 4	760
	11th to 20th	Night	20% 11% 27% 29% 11% 1	760
	21st to end	Night	21% 12% 32% 27% 8%	836
November	1st to 10th	Night	16% 10% 33% 26% 14% 1	780
	11th to 20th	Night	21% 16% 31% 24% 7% 1	800
	21st to end	Night	25% 14% 31% 24% 6% 1	800
December	1st to 10th	Night	24% 15% 34% 22% 5%	800
	11th to 20th	Night	25% 14% 33% 23% 6%	910
	21st to end	Night	31% 15% 32% 19% 3	1100

Page generated at 2025-02-03 03:05:56. Version ac07

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