North-South Lake
Clear Sky Chart
History

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

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% 8% 3 7% 5% 5% 5% 4 6% 8% 35%	101388
	Night	15% 8% 3 7% 5% 4 4 3 5% 7% 39%	97683
Transparency	Day	43% 7% 14% 22% 13% 2	104894
	Night	43% 6% 14% 23% 13% 2	102253
Seeing	Day	19% 15% 31% 23% 10% 3	14870
	Night	19% 12% 32% 27% 9% 1	23950

By Month

Percentage Cloud Cover NE (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% 9% 4 9% 5% 5% 5% 3 5% 6% 37%	2517
	11th to 20th	Day	11% 12% 5% 11% 7% 5% 5% 4 5% 6% 29%	2520
	21st to end	Day	12% 12% 5% 14% 6% 5% 4 4 5% 5% 28%	2914
February	1st to 10th	Day	12% 12% 4 9% 6% 5% 5% 4 6% 7% 30%	1710
	11th to 20th	Day	11% 8% 4 8% 6% 5% 5% 4 6% 6% 37%	1821
	21st to end	Day	16% 12% 3 6% 5% 5% 3 5% 5% 5% 35%	1570
March	1st to 10th	Day	21% 11% 4 9% 5% 4 4 3 4 5% 31%	3116
	11th to 20th	Day	9% 9% 3 8% 5% 6% 5% 4 6% 7% 38%	3320
	21st to end	Day	19% 10% 2 5% 4 3 4 3 5% 6% 39%	4134
April	1st to 10th	Day	16% 12% 3 7% 5% 4 4 3 5% 5% 35%	2280
	11th to 20th	Day	15% 8% 2 7% 5% 4 5% 4 6% 6% 38%	2254
	21st to end	Day	18% 7% 3 7% 4 5% 5% 4 5% 7% 36%	2340
May	1st to 10th	Day	22% 10% 3 7% 5% 4 5% 3 5% 7% 29%	4184
	11th to 20th	Day	20% 7% 2 6% 5% 5% 4 4 6% 7% 33%	4398
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 5% 7% 10% 41%	4837
June	1st to 10th	Day	15% 8% 2 7% 5% 5% 5% 5% 7% 9% 32%	2660
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 4 7% 9% 34%	2660
	21st to end	Day	15% 6% 2 7% 5% 6% 6% 5% 7% 10% 32%	2660
July	1st to 10th	Day	7% 5% 2 8% 6% 7% 7% 5% 9% 10% 33%	4440
	11th to 20th	Day	8% 5% 2 7% 6% 6% 7% 6% 8% 12% 34%	4440
	21st to end	Day	12% 7% 3 8% 6% 6% 6% 5% 7% 8% 34%	4814
August	1st to 10th	Day	16% 7% 3 7% 6% 5% 6% 5% 7% 8% 30%	4325
	11th to 20th	Day	12% 7% 3 7% 5% 5% 6% 4 8% 10% 33%	3730
	21st to end	Day	8% 4 2 7% 5% 6% 7% 5% 8% 10% 38%	4180
September	1st to 10th	Day	13% 6% 3 6% 5% 5% 5% 4 5% 7% 42%	2280
	11th to 20th	Day	12% 4 2 6% 4 4 4 3 5% 6% 48%	2201
	21st to end	Day	15% 6% 2 6% 3 4 6% 4 6% 7% 41%	2090
October	1st to 10th	Day	17% 7% 2 6% 5% 4 5% 4 5% 6% 39%	1971
	11th to 20th	Day	13% 8% 2 7% 4 4 4 3 6% 7% 42%	1900
	21st to end	Day	20% 8% 3 5% 5% 5% 5% 5% 6% 6% 34%	1911
November	1st to 10th	Day	12% 7% 3 6% 4 4 4 3 6% 6% 45%	1734
	11th to 20th	Day	15% 8% 3 6% 6% 4 4 4 5% 6% 39%	1710
	21st to end	Day	15% 8% 3 6% 6% 5% 5% 5% 5% 6% 36%	1569
December	1st to 10th	Day	13% 10% 4 12% 6% 6% 6% 4 6% 7% 27%	1520
	11th to 20th	Day	20% 8% 4 6% 5% 3 4 3 6% 5% 36%	1906
	21st to end	Day	19% 11% 4 9% 5% 5% 4 4 5% 8% 26%	2772
January	1st to 10th	Night	14% 10% 3 7% 4 3 4 3 5% 6% 41%	4429
	11th to 20th	Night	11% 13% 5% 11% 6% 4 4 3 5% 6% 32%	4440
	21st to end	Night	18% 13% 4 9% 6% 5% 5% 3 4 5% 28%	4724
February	1st to 10th	Night	12% 9% 4 9% 7% 6% 5% 4 5% 5% 34%	2470
	11th to 20th	Night	10% 11% 3 7% 6% 5% 6% 4 6% 7% 36%	2244
	21st to end	Night	15% 9% 3 7% 4 5% 4 4 5% 6% 37%	1884
March	1st to 10th	Night	23% 10% 2 6% 3 4 4 3 5% 6% 34%	3724
	11th to 20th	Night	11% 9% 3 6% 5% 6% 6% 4 6% 7% 38%	3621
	21st to end	Night	14% 9% 3 8% 5% 4 5% 3 5% 6% 39%	3483
April	1st to 10th	Night	15% 9% 3 7% 6% 5% 6% 5% 6% 6% 33%	1900
	11th to 20th	Night	17% 8% 3 5% 4 4 4 4 5% 6% 39%	1875
	21st to end	Night	19% 7% 2 6% 4 4 4 3 5% 6% 40%	1838
May	1st to 10th	Night	22% 9% 3 7% 4 5% 4 3 5% 7% 32%	2784
	11th to 20th	Night	19% 9% 3 6% 4 4 4 4 5% 6% 35%	2495
	21st to end	Night	12% 6% 2 5% 4 4 6% 4 6% 9% 40%	2738
June	1st to 10th	Night	15% 6% 3 6% 5% 4 3 4 6% 7% 42%	1520
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 7% 9% 42%	1520
	21st to end	Night	11% 4 2 6% 5% 5% 5% 3 7% 9% 44%	1520
July	1st to 10th	Night	9% 5% 2 5% 5% 5% 5% 4 7% 8% 44%	2520
	11th to 20th	Night	12% 5% 3 6% 4 5% 4 4 6% 9% 42%	2520
	21st to end	Night	13% 7% 2 6% 4 5% 5% 5% 6% 6% 41%	2739
August	1st to 10th	Night	17% 6% 2 6% 5% 5% 5% 4 6% 8% 36%	2584
	11th to 20th	Night	13% 6% 3 7% 4 4 4 3 5% 8% 42%	3084
	21st to end	Night	9% 4 2 4 4 4 4 3 5% 7% 53%	3476
September	1st to 10th	Night	13% 5% 2 5% 4 4 4 4 6% 8% 45%	1900
	11th to 20th	Night	14% 4 1 4 3 3 3 2 4 7% 55%	1978
	21st to end	Night	15% 6% 2 7% 4 3 4 3 5% 6% 45%	2090
October	1st to 10th	Night	19% 6% 3 7% 4 3 4 2 5% 7% 41%	2204
	11th to 20th	Night	16% 6% 2 6% 4 4 4 4 5% 6% 44%	2280
	21st to end	Night	21% 8% 2 5% 5% 4 4 3 5% 7% 37%	2685
November	1st to 10th	Night	12% 8% 3 6% 4 3 3 3 5% 6% 46%	2505
	11th to 20th	Night	16% 8% 3 6% 4 4 4 3 6% 6% 40%	2470
	21st to end	Night	13% 7% 3 6% 5% 4 4 4 5% 8% 41%	2607
December	1st to 10th	Night	15% 10% 3 8% 5% 5% 4 3 6% 6% 34%	2660
	11th to 20th	Night	18% 8% 3 6% 5% 4 4 4 6% 7% 35%	3288
	21st to end	Night	20% 10% 3 8% 5% 4 4 3 5% 6% 30%	4884

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	43% 4 19% 24% 7% 2	2518
	11th to 20th	Day	53% 7% 14% 18% 8% 1	2520
	21st to end	Day	56% 5% 13% 18% 7% 1	2914
February	1st to 10th	Day	51% 6% 14% 18% 9% 2	1710
	11th to 20th	Day	44% 7% 10% 23% 13% 3	1830
	21st to end	Day	49% 5% 12% 20% 12% 2	1570
March	1st to 10th	Day	54% 5% 13% 16% 10% 2	3119
	11th to 20th	Day	40% 7% 20% 22% 10% 2	3320
	21st to end	Day	45% 5% 7% 17% 22% 4	4134
April	1st to 10th	Day	49% 6% 10% 21% 12% 3	2280
	11th to 20th	Day	43% 6% 12% 21% 15% 2	2254
	21st to end	Day	45% 5% 13% 19% 15% 4	2340
May	1st to 10th	Day	52% 7% 12% 18% 11% 1	4198
	11th to 20th	Day	48% 7% 15% 21% 8% 1	4402
	21st to end	Day	35% 8% 16% 27% 14% 2	4837
June	1st to 10th	Day	44% 7% 17% 19% 13% 1	2660
	11th to 20th	Day	41% 8% 17% 22% 11% 1	2660
	21st to end	Day	42% 9% 14% 23% 10% 1	2660
July	1st to 10th	Day	39% 10% 16% 20% 15% 1	4370
	11th to 20th	Day	38% 8% 19% 23% 11% 1	4365
	21st to end	Day	44% 8% 14% 19% 14% 1	4661
August	1st to 10th	Day	47% 7% 16% 20% 9% 1	4311
	11th to 20th	Day	41% 7% 17% 28% 7%	3766
	21st to end	Day	35% 7% 17% 27% 12% 1	4180
September	1st to 10th	Day	40% 6% 13% 24% 16% 1	2280
	11th to 20th	Day	35% 5% 11% 25% 22% 2	2201
	21st to end	Day	40% 5% 13% 23% 16% 2	2090
October	1st to 10th	Day	39% 5% 10% 22% 22% 2	3270
	11th to 20th	Day	31% 4 9% 29% 24% 3	3140
	21st to end	Day	32% 6% 15% 28% 15% 4	3123
November	1st to 10th	Day	37% 6% 14% 26% 15% 2	1734
	11th to 20th	Day	45% 5% 13% 21% 15% 2	1710
	21st to end	Day	45% 5% 16% 24% 8% 2	1569
December	1st to 10th	Day	55% 5% 15% 16% 9% 1	1520
	11th to 20th	Day	47% 6% 16% 21% 8% 2	1906
	21st to end	Day	56% 8% 13% 16% 6%	2772
January	1st to 10th	Night	43% 6% 17% 22% 11% 2	4429
	11th to 20th	Night	52% 7% 12% 18% 10% 2	4440
	21st to end	Night	56% 5% 13% 17% 8% 1	4724
February	1st to 10th	Night	49% 5% 15% 20% 10% 2	2470
	11th to 20th	Night	46% 7% 11% 21% 14% 2	2246
	21st to end	Night	45% 5% 12% 23% 11% 3	1884
March	1st to 10th	Night	50% 6% 11% 20% 11% 1	3734
	11th to 20th	Night	42% 7% 18% 22% 10% 1	3622
	21st to end	Night	44% 7% 8% 18% 20% 3	3483
April	1st to 10th	Night	49% 5% 12% 20% 12% 2	1900
	11th to 20th	Night	45% 6% 11% 20% 17% 1	1875
	21st to end	Night	46% 5% 11% 21% 15% 3	1838
May	1st to 10th	Night	52% 6% 12% 17% 11% 2	2790
	11th to 20th	Night	48% 8% 14% 19% 9% 1	2496
	21st to end	Night	38% 8% 17% 22% 13% 2	2739
June	1st to 10th	Night	40% 7% 12% 25% 14% 2	1520
	11th to 20th	Night	37% 7% 18% 26% 11% 1	1520
	21st to end	Night	35% 8% 16% 25% 15% 1	1520
July	1st to 10th	Night	35% 8% 18% 21% 16% 2	2480
	11th to 20th	Night	37% 8% 16% 25% 14%	2472
	21st to end	Night	42% 7% 13% 21% 15% 2	2651
August	1st to 10th	Night	44% 8% 17% 21% 9% 1	2574
	11th to 20th	Night	38% 8% 16% 28% 10%	3114
	21st to end	Night	29% 6% 12% 38% 15% 1	3476
September	1st to 10th	Night	37% 7% 10% 29% 16% 1	1900
	11th to 20th	Night	31% 4 11% 28% 24% 1	1978
	21st to end	Night	40% 4 12% 24% 19% 1	2090
October	1st to 10th	Night	39% 7% 13% 23% 18% 1	3672
	11th to 20th	Night	30% 3 11% 27% 25% 4	3779
	21st to end	Night	35% 5% 15% 31% 13% 2	4423
November	1st to 10th	Night	37% 7% 12% 25% 17% 3	2505
	11th to 20th	Night	43% 6% 13% 22% 13% 3	2470
	21st to end	Night	41% 5% 18% 27% 8% 1	2607
December	1st to 10th	Night	48% 6% 15% 21% 9% 1	2660
	11th to 20th	Night	47% 6% 16% 17% 12% 1	3288
	21st to end	Night	53% 6% 15% 19% 7%	4884

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	20% 18% 39% 16% 7%	180
	11th to 20th	Day	24% 26% 36% 12% 2 1	180
	21st to end	Day	17% 22% 41% 16% 4	240
February	1st to 10th	Day	29% 21% 39% 10% 1	270
	11th to 20th	Day	24% 27% 36% 12% 1	429
	21st to end	Day	27% 23% 32% 15% 2	382
March	1st to 10th	Day	24% 18% 37% 18% 3	460
	11th to 20th	Day	21% 24% 36% 16% 3 1	460
	21st to end	Day	27% 25% 26% 15% 5% 2	506
April	1st to 10th	Day	27% 23% 28% 15% 7% 1	460
	11th to 20th	Day	23% 24% 30% 15% 7% 1	452
	21st to end	Day	27% 16% 34% 16% 6% 2	460
May	1st to 10th	Day	29% 17% 29% 17% 8% 1	463
	11th to 20th	Day	20% 14% 35% 21% 9% 2	487
	21st to end	Day	17% 9% 32% 26% 13% 3	529
June	1st to 10th	Day	16% 9% 34% 25% 12% 3	490
	11th to 20th	Day	14% 12% 31% 30% 11% 2	490
	21st to end	Day	17% 10% 30% 28% 13% 2	490
July	1st to 10th	Day	11% 5% 33% 32% 17% 2	485
	11th to 20th	Day	10% 6% 26% 39% 15% 4	484
	21st to end	Day	13% 6% 33% 31% 15% 2	532
August	1st to 10th	Day	10% 6% 28% 35% 15% 5%	486
	11th to 20th	Day	14% 5% 25% 35% 14% 7%	479
	21st to end	Day	11% 6% 29% 32% 15% 7%	539
September	1st to 10th	Day	17% 8% 25% 27% 16% 7%	490
	11th to 20th	Day	13% 9% 27% 24% 17% 10%	490
	21st to end	Day	19% 10% 27% 28% 12% 4	490
October	1st to 10th	Day	23% 11% 24% 23% 14% 5%	490
	11th to 20th	Day	14% 17% 31% 28% 8% 2	490
	21st to end	Day	23% 17% 33% 21% 6%	444
November	1st to 10th	Day	18% 19% 30% 21% 11% 1	386
	11th to 20th	Day	21% 21% 31% 21% 5% 1	370
	21st to end	Day	18% 19% 38% 21% 3 1	229
December	1st to 10th	Day	20% 21% 41% 12% 6% 1	180
	11th to 20th	Day	27% 24% 33% 12% 4	180
	21st to end	Day	23% 19% 41% 15% 2 1	198
January	1st to 10th	Night	18% 16% 41% 22% 3	760
	11th to 20th	Night	19% 18% 37% 24% 2	760
	21st to end	Night	17% 18% 40% 24% 2	836
February	1st to 10th	Night	18% 19% 39% 22% 2	760
	11th to 20th	Night	18% 19% 43% 19% 1	743
	21st to end	Night	23% 16% 40% 19% 3	628
March	1st to 10th	Night	20% 17% 38% 21% 3	760
	11th to 20th	Night	20% 15% 42% 19% 3	760
	21st to end	Night	20% 21% 33% 20% 6%	836
April	1st to 10th	Night	20% 18% 36% 22% 4	760
	11th to 20th	Night	22% 16% 35% 21% 6%	751
	21st to end	Night	22% 15% 31% 25% 6% 1	698
May	1st to 10th	Night	26% 13% 29% 24% 8%	546
	11th to 20th	Night	17% 11% 32% 32% 7% 1	374
	21st to end	Night	16% 7% 28% 37% 11%	411
June	1st to 10th	Night	18% 6% 30% 34% 13% 1	380
	11th to 20th	Night	15% 7% 27% 36% 14% 1	380
	21st to end	Night	13% 4 27% 42% 14% 1	380
July	1st to 10th	Night	14% 3 22% 41% 19% 1	370
	11th to 20th	Night	14% 3 21% 42% 19% 1	368
	21st to end	Night	13% 4 20% 46% 16% 1	416
August	1st to 10th	Night	11% 3 19% 45% 20% 2	417
	11th to 20th	Night	13% 4 17% 40% 22% 3	737
	21st to end	Night	16% 5% 18% 37% 23% 2	836
September	1st to 10th	Night	17% 4 25% 34% 17% 2	760
	11th to 20th	Night	16% 6% 24% 28% 20% 6%	760
	21st to end	Night	18% 6% 24% 35% 14% 2	760
October	1st to 10th	Night	22% 9% 24% 28% 14% 3	760
	11th to 20th	Night	20% 9% 31% 32% 8%	760
	21st to end	Night	25% 12% 30% 26% 6%	836
November	1st to 10th	Night	17% 14% 33% 27% 8%	771
	11th to 20th	Night	21% 12% 36% 24% 6% 1	760
	21st to end	Night	16% 15% 36% 27% 6% 1	760
December	1st to 10th	Night	21% 14% 38% 22% 4	760
	11th to 20th	Night	21% 13% 38% 25% 3	760
	21st to end	Night	23% 16% 41% 19% 2	836

Page generated at 2024-11-05 08:15:51. Version ac07

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