Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Point clear sky chart from 2005-11-06 to 2026-03-03.

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 6% 4 4 4 4 5% 7% 44%	130643
	Night	13% 6% 2 5% 4 4 4 3 5% 7% 47%	130703
Transparency	Day	39% 4 10% 21% 19% 7%	134250
	Night	36% 4 10% 20% 21% 9%	135174
Seeing	Day	14% 8% 22% 25% 22% 8%	16850
	Night	15% 7% 24% 32% 20% 3	26746

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	18% 10% 3 6% 3 3 3 3 5% 5% 42%	5289
	11th to 20th	Day	14% 5% 2 4 2 2 2 2 4 7% 57%	5310
	21st to end	Day	25% 9% 3 6% 3 2 2 2 3 3 43%	5812
February	1st to 10th	Day	20% 9% 3 6% 4 3 3 3 4 5% 40%	1907
	11th to 20th	Day	21% 9% 3 6% 4 3 4 2 4 5% 39%	2048
	21st to end	Day	21% 7% 3 6% 4 4 3 3 3 6% 39%	1814
March	1st to 10th	Day	20% 10% 3 8% 4 4 4 2 4 5% 35%	4958
	11th to 20th	Day	13% 6% 2 6% 3 3 4 3 5% 7% 48%	4980
	21st to end	Day	15% 8% 3 8% 5% 4 4 3 5% 5% 41%	5462
April	1st to 10th	Day	14% 7% 2 6% 4 5% 4 4 5% 6% 43%	2393
	11th to 20th	Day	17% 7% 2 6% 3 4 4 3 5% 6% 42%	2374
	21st to end	Day	11% 5% 3 6% 5% 4 5% 3 6% 7% 45%	2400
May	1st to 10th	Day	16% 8% 3 7% 5% 5% 4 4 6% 7% 36%	5405
	11th to 20th	Day	12% 6% 3 8% 5% 5% 5% 4 6% 8% 37%	5482
	21st to end	Day	10% 5% 2 6% 5% 6% 5% 4 7% 10% 39%	6434
June	1st to 10th	Day	9% 4 2 6% 5% 6% 6% 6% 8% 10% 39%	2600
	11th to 20th	Day	6% 5% 2 5% 5% 5% 5% 6% 7% 9% 44%	2600
	21st to end	Day	5% 4 2 4 6% 5% 7% 6% 8% 10% 42%	2600
July	1st to 10th	Day	6% 5% 2 9% 7% 7% 7% 6% 8% 10% 32%	5900
	11th to 20th	Day	7% 4 2 6% 4 5% 6% 5% 7% 10% 44%	5900
	21st to end	Day	12% 7% 2 6% 4 5% 5% 5% 8% 10% 37%	6422
August	1st to 10th	Day	3 2 1 3 3 3 4 3 5% 7% 65%	4107
	11th to 20th	Day	5% 3 1 5% 4 4 5% 4 7% 12% 50%	3849
	21st to end	Day	9% 4 2 7% 5% 5% 5% 4 5% 7% 46%	4312
September	1st to 10th	Day	9% 5% 2 5% 5% 5% 6% 4 7% 8% 45%	2400
	11th to 20th	Day	13% 5% 2 6% 4 5% 5% 4 5% 8% 44%	2400
	21st to end	Day	9% 4 2 4 4 4 4 4 5% 7% 54%	2096
October	1st to 10th	Day	6% 4 1 5% 4 3 3 3 5% 5% 60%	2000
	11th to 20th	Day	11% 4 2 4 3 3 2 3 3 6% 59%	2000
	21st to end	Day	15% 5% 2 6% 2 3 3 3 4 5% 53%	2200
November	1st to 10th	Day	13% 6% 2 4 3 3 3 3 3 5% 54%	2058
	11th to 20th	Day	11% 6% 2 4 4 3 4 3 3 5% 54%	2100
	21st to end	Day	15% 7% 3 6% 4 4 3 3 4 6% 45%	2061
December	1st to 10th	Day	19% 7% 3 6% 3 4 4 2 3 4 46%	2902
	11th to 20th	Day	17% 10% 3 6% 4 3 3 3 4 5% 42%	3481
	21st to end	Day	16% 7% 2 6% 3 3 3 2 4 7% 46%	4587
January	1st to 10th	Night	17% 7% 2 5% 3 3 3 3 4 4 49%	7634
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 4 6% 53%	7680
	21st to end	Night	27% 7% 2 6% 4 3 3 2 4 4 37%	8402
February	1st to 10th	Night	16% 7% 3 6% 4 4 3 3 4 6% 45%	2709
	11th to 20th	Night	20% 9% 2 6% 4 3 4 2 4 5% 42%	2458
	21st to end	Night	20% 8% 2 6% 3 3 3 3 3 5% 43%	2009
March	1st to 10th	Night	17% 8% 3 7% 5% 4 4 3 4 5% 41%	4941
	11th to 20th	Night	13% 6% 2 5% 3 4 3 3 6% 7% 49%	4980
	21st to end	Night	17% 7% 2 6% 4 4 4 4 4 6% 42%	5467
April	1st to 10th	Night	13% 5% 2 3 3 4 4 4 6% 7% 49%	2005
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 5% 6% 47%	1975
	21st to end	Night	10% 5% 3 6% 4 4 3 4 5% 6% 51%	2000
May	1st to 10th	Night	14% 8% 3 6% 5% 4 4 3 6% 8% 37%	4490
	11th to 20th	Night	16% 6% 3 7% 5% 5% 4 4 6% 9% 35%	4411
	21st to end	Night	10% 6% 2 6% 5% 5% 4 4 6% 9% 43%	4443
June	1st to 10th	Night	7% 3 2 6% 3 4 5% 5% 7% 10% 48%	1800
	11th to 20th	Night	5% 4 1 4 3 3 4 5% 7% 10% 54%	1800
	21st to end	Night	5% 4 2 4 3 3 4 5% 6% 9% 54%	1800
July	1st to 10th	Night	4 5% 2 7% 5% 6% 7% 6% 8% 10% 38%	4078
	11th to 20th	Night	6% 3 1 4 4 4 5% 5% 8% 12% 47%	4077
	21st to end	Night	10% 6% 2 5% 4 4 4 4 6% 12% 43%	4449
August	1st to 10th	Night	2 1 1 2 2 3 3 3 6% 7% 70%	3046
	11th to 20th	Night	4 3 1 4 3 4 5% 5% 8% 13% 51%	3200
	21st to end	Night	6% 4 2 5% 4 4 5% 4 7% 8% 51%	3586
September	1st to 10th	Night	7% 4 2 6% 4 5% 4 5% 5% 7% 52%	2000
	11th to 20th	Night	10% 5% 2 5% 4 4 5% 4 6% 8% 47%	2000
	21st to end	Night	8% 4 2 4 3 3 3 3 5% 6% 60%	2278
October	1st to 10th	Night	7% 3 1 4 3 3 3 3 5% 6% 62%	2400
	11th to 20th	Night	10% 4 1 4 3 3 2 3 4 5% 60%	2400
	21st to end	Night	12% 4 2 4 3 3 3 3 3 6% 57%	2640
November	1st to 10th	Night	13% 4 2 4 3 3 3 3 4 5% 56%	2460
	11th to 20th	Night	12% 5% 2 4 3 2 3 2 4 6% 56%	2520
	21st to end	Night	14% 6% 2 5% 4 3 4 3 3 5% 49%	2538
December	1st to 10th	Night	20% 7% 2 5% 3 3 3 3 4 5% 46%	4448
	11th to 20th	Night	16% 7% 2 7% 4 4 4 3 3 4 45%	4946
	21st to end	Night	16% 9% 2 5% 3 3 3 3 4 5% 48%	6633

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	46% 1 6% 26% 18% 3	5290
	11th to 20th	Day	30% 1 4 27% 30% 7%	5310
	21st to end	Day	50% 2 3 12% 22% 12%	5812
February	1st to 10th	Day	46% 3 7% 17% 17% 9%	1907
	11th to 20th	Day	50% 3 6% 17% 18% 7%	2058
	21st to end	Day	49% 2 7% 12% 20% 10%	1814
March	1st to 10th	Day	52% 3 5% 14% 17% 9%	4958
	11th to 20th	Day	37% 3 6% 17% 22% 15%	4980
	21st to end	Day	46% 3 8% 20% 18% 5%	5464
April	1st to 10th	Day	42% 4 8% 21% 17% 8%	2393
	11th to 20th	Day	42% 4 10% 15% 19% 8%	2374
	21st to end	Day	38% 4 10% 23% 21% 3	2400
May	1st to 10th	Day	48% 4 10% 25% 12% 2	5440
	11th to 20th	Day	44% 4 14% 18% 19% 1	5486
	21st to end	Day	40% 5% 13% 25% 16% 2	6447
June	1st to 10th	Day	37% 8% 15% 24% 15% 1	2600
	11th to 20th	Day	34% 7% 14% 26% 17% 2	2600
	21st to end	Day	33% 9% 16% 24% 15% 3	2600
July	1st to 10th	Day	45% 4 21% 21% 8%	5836
	11th to 20th	Day	35% 4 21% 31% 9%	5831
	21st to end	Day	42% 4 18% 27% 9%	6240
August	1st to 10th	Day	19% 5% 12% 30% 29% 4	4093
	11th to 20th	Day	27% 5% 21% 34% 12% 1	3885
	21st to end	Day	38% 5% 13% 23% 20% 2	4311
September	1st to 10th	Day	36% 7% 12% 20% 18% 7%	2400
	11th to 20th	Day	38% 6% 10% 21% 19% 5%	2400
	21st to end	Day	29% 5% 9% 23% 24% 10%	2096
October	1st to 10th	Day	17% 2 5% 14% 25% 38%	3260
	11th to 20th	Day	18% 2 3 16% 33% 28%	3240
	21st to end	Day	28% 1 3 18% 36% 13%	3538
November	1st to 10th	Day	34% 4 7% 17% 27% 10%	2058
	11th to 20th	Day	33% 3 6% 18% 26% 13%	2100
	21st to end	Day	42% 3 6% 18% 23% 8%	2061
December	1st to 10th	Day	45% 2 5% 20% 23% 5%	2902
	11th to 20th	Day	48% 2 4 18% 19% 9%	3479
	21st to end	Day	40% 2 6% 19% 29% 3	4587
January	1st to 10th	Night	40% 2 7% 25% 22% 4	7635
	11th to 20th	Night	35% 2 4 18% 31% 10%	7680
	21st to end	Night	53% 2 5% 14% 18% 8%	8402
February	1st to 10th	Night	42% 3 6% 19% 22% 9%	2709
	11th to 20th	Night	47% 3 6% 18% 19% 8%	2459
	21st to end	Night	44% 4 6% 14% 17% 15%	2009
March	1st to 10th	Night	47% 3 6% 12% 22% 11%	4941
	11th to 20th	Night	36% 4 7% 16% 20% 17%	4980
	21st to end	Night	43% 4 8% 18% 21% 6%	5467
April	1st to 10th	Night	33% 5% 10% 21% 19% 10%	2005
	11th to 20th	Night	37% 4 10% 17% 22% 11%	1975
	21st to end	Night	34% 4 7% 24% 25% 5%	2000
May	1st to 10th	Night	45% 4 11% 22% 15% 3	4520
	11th to 20th	Night	46% 4 13% 22% 14% 1	4412
	21st to end	Night	38% 4 16% 23% 15% 4	4452
June	1st to 10th	Night	29% 8% 18% 26% 18% 2	1800
	11th to 20th	Night	24% 7% 18% 28% 18% 4	1800
	21st to end	Night	25% 8% 16% 28% 19% 4	1800
July	1st to 10th	Night	39% 6% 23% 22% 9% 1	4035
	11th to 20th	Night	28% 6% 28% 28% 10% 1	4026
	21st to end	Night	36% 5% 19% 27% 12% 1	4320
August	1st to 10th	Night	14% 4 16% 31% 31% 4	3036
	11th to 20th	Night	25% 4 20% 36% 14% 2	3230
	21st to end	Night	31% 6% 13% 22% 25% 4	3586
September	1st to 10th	Night	31% 8% 13% 21% 19% 9%	2000
	11th to 20th	Night	35% 6% 11% 18% 21% 9%	2000
	21st to end	Night	26% 3 9% 23% 25% 13%	2278
October	1st to 10th	Night	18% 2 5% 15% 22% 38%	3920
	11th to 20th	Night	18% 2 3 15% 31% 30%	3899
	21st to end	Night	23% 2 5% 15% 37% 17%	4252
November	1st to 10th	Night	32% 4 7% 19% 25% 13%	2460
	11th to 20th	Night	30% 3 8% 18% 28% 13%	2520
	21st to end	Night	39% 3 6% 17% 25% 10%	2538
December	1st to 10th	Night	44% 2 5% 20% 25% 4	4448
	11th to 20th	Night	45% 2 6% 16% 23% 8%	4947
	21st to end	Night	41% 3 6% 21% 26% 4	6633

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	24% 16% 37% 18% 4 1	330
	11th to 20th	Day	22% 21% 37% 14% 5% 1	330
	21st to end	Day	23% 22% 35% 17% 3	363
February	1st to 10th	Day	26% 14% 39% 16% 5% 1	330
	11th to 20th	Day	33% 17% 35% 12% 2	330
	21st to end	Day	30% 23% 35% 8% 4	273
March	1st to 10th	Day	25% 16% 34% 21% 5%	306
	11th to 20th	Day	20% 21% 40% 18% 1 1	300
	21st to end	Day	20% 20% 38% 17% 5%	330
April	1st to 10th	Day	20% 16% 34% 21% 8%	493
	11th to 20th	Day	24% 13% 29% 22% 11% 2	492
	21st to end	Day	15% 14% 29% 26% 14% 2	500
May	1st to 10th	Day	16% 10% 31% 27% 14% 2	503
	11th to 20th	Day	15% 8% 24% 30% 18% 5%	553
	21st to end	Day	9% 4 24% 35% 22% 6%	789
June	1st to 10th	Day	9% 4 14% 35% 26% 11%	730
	11th to 20th	Day	7% 2 15% 36% 33% 8%	730
	21st to end	Day	7% 1 12% 31% 34% 15%	730
July	1st to 10th	Day	6% 2 9% 27% 41% 15%	721
	11th to 20th	Day	7% 1 7% 26% 40% 19%	718
	21st to end	Day	7% 1 8% 26% 41% 17%	794
August	1st to 10th	Day	6% 1 7% 26% 42% 18%	651
	11th to 20th	Day	8% 1 5% 21% 45% 20%	519
	21st to end	Day	13% 2 7% 21% 34% 24%	583
September	1st to 10th	Day	8% 2 9% 27% 38% 17%	530
	11th to 20th	Day	13% 2 9% 22% 34% 20%	530
	21st to end	Day	10% 7% 13% 31% 28% 12%	356
October	1st to 10th	Day	6% 2 25% 38% 22% 7%	330
	11th to 20th	Day	8% 5% 30% 32% 20% 5%	330
	21st to end	Day	20% 7% 32% 21% 17% 4	363
November	1st to 10th	Day	22% 10% 23% 28% 14% 3	330
	11th to 20th	Day	12% 8% 39% 30% 9% 2	330
	21st to end	Day	18% 15% 35% 21% 9% 2	330
December	1st to 10th	Day	20% 12% 42% 17% 7% 1	330
	11th to 20th	Day	24% 13% 34% 21% 8% 1	330
	21st to end	Day	21% 15% 36% 20% 6% 2	363
January	1st to 10th	Night	22% 11% 33% 29% 5%	1050
	11th to 20th	Night	23% 13% 34% 24% 7%	1050
	21st to end	Night	24% 9% 34% 30% 3	1155
February	1st to 10th	Night	21% 10% 35% 29% 5%	1029
	11th to 20th	Night	24% 13% 34% 26% 3	823
	21st to end	Night	24% 16% 33% 23% 3	625
March	1st to 10th	Night	17% 11% 34% 32% 6%	606
	11th to 20th	Night	19% 12% 34% 30% 5% 1	600
	21st to end	Night	17% 9% 36% 28% 9%	660
April	1st to 10th	Night	16% 10% 38% 29% 8%	600
	11th to 20th	Night	17% 9% 34% 27% 11% 1	593
	21st to end	Night	12% 9% 32% 34% 12% 1	600
May	1st to 10th	Night	12% 5% 29% 41% 12% 1	600
	11th to 20th	Night	12% 6% 27% 33% 21% 2	591
	21st to end	Night	8% 3 20% 40% 26% 4	650
June	1st to 10th	Night	8% 2 11% 40% 33% 6%	600
	11th to 20th	Night	6% 2 11% 36% 41% 4	600
	21st to end	Night	6% 1 7% 34% 42% 10%	600
July	1st to 10th	Night	5% 2 5% 30% 47% 11%	585
	11th to 20th	Night	5% 1 5% 27% 51% 10%	582
	21st to end	Night	5% 1 4 30% 46% 14%	657
August	1st to 10th	Night	3 1 5% 30% 49% 12%	597
	11th to 20th	Night	6% 2 4 31% 48% 8%	594
	21st to end	Night	11% 1 6% 25% 44% 13%	660
September	1st to 10th	Night	7% 1 8% 35% 41% 7%	600
	11th to 20th	Night	12% 2 9% 30% 39% 9%	600
	21st to end	Night	8% 3 11% 36% 37% 4	709
October	1st to 10th	Night	7% 2 15% 38% 33% 5%	800
	11th to 20th	Night	11% 4 22% 38% 23% 2	800
	21st to end	Night	14% 5% 24% 35% 18% 3	880
November	1st to 10th	Night	15% 5% 23% 34% 21% 3	820
	11th to 20th	Night	14% 6% 26% 39% 14%	840
	21st to end	Night	15% 9% 32% 30% 13% 1	840
December	1st to 10th	Night	21% 9% 29% 32% 9%	945
	11th to 20th	Night	22% 8% 30% 30% 8%	1050
	21st to end	Night	24% 12% 27% 29% 7% 1	1155

Page generated at 2026-02-28 00:40:20. Version ac07

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