Halibut Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Halibut Point clear sky chart from 2005-11-06 to 2026-03-18.

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	16% 7% 2 6% 4 4 4 4 5% 7% 40%	130668
	Night	17% 8% 3 6% 4 4 4 3 5% 6% 39%	130818
Transparency	Day	45% 4 11% 23% 15% 2	134202
	Night	45% 3 11% 22% 16% 3	135371
Seeing	Day	21% 15% 32% 22% 8% 2	16739
	Night	21% 12% 33% 25% 8% 1	25702

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	11% 7% 3 8% 5% 5% 4 4 6% 7% 40%	4661
	11th to 20th	Day	16% 9% 3 5% 3 3 3 3 5% 6% 45%	4650
	21st to end	Day	14% 8% 2 5% 4 3 3 3 4 6% 47%	5124
February	1st to 10th	Day	18% 9% 3 6% 4 4 4 4 5% 6% 37%	1945
	11th to 20th	Day	14% 7% 2 7% 4 4 5% 4 6% 8% 40%	2048
	21st to end	Day	15% 9% 3 6% 5% 3 5% 3 6% 6% 38%	1730
March	1st to 10th	Day	20% 10% 2 7% 4 4 4 3 5% 6% 35%	4576
	11th to 20th	Day	16% 10% 3 7% 4 4 4 4 6% 7% 36%	4914
	21st to end	Day	28% 7% 2 5% 4 4 4 3 6% 6% 31%	5665
April	1st to 10th	Day	19% 8% 3 6% 4 4 4 3 4 6% 38%	2400
	11th to 20th	Day	17% 7% 2 6% 4 4 4 4 5% 7% 40%	2427
	21st to end	Day	19% 5% 2 6% 4 5% 4 5% 5% 7% 39%	2600
May	1st to 10th	Day	27% 11% 3 6% 4 3 4 3 5% 7% 27%	5886
	11th to 20th	Day	18% 10% 3 8% 5% 5% 5% 3 5% 6% 32%	5861
	21st to end	Day	19% 7% 2 6% 4 4 4 3 5% 7% 38%	6949
June	1st to 10th	Day	19% 7% 2 6% 4 4 5% 4 6% 8% 36%	2800
	11th to 20th	Day	15% 6% 2 6% 5% 4 4 4 6% 9% 41%	2800
	21st to end	Day	16% 5% 2 6% 5% 4 4 5% 7% 8% 38%	2800
July	1st to 10th	Day	15% 8% 3 7% 4 5% 5% 4 7% 9% 34%	6360
	11th to 20th	Day	6% 7% 2 6% 5% 5% 5% 4 7% 11% 41%	6360
	21st to end	Day	13% 6% 2 5% 4 4 4 4 5% 8% 46%	6909
August	1st to 10th	Day	13% 6% 3 6% 5% 5% 5% 5% 6% 8% 38%	4235
	11th to 20th	Day	13% 8% 3 7% 4 4 4 4 6% 7% 40%	4175
	21st to end	Day	7% 3 1 4 3 5% 5% 5% 8% 10% 49%	4355
September	1st to 10th	Day	13% 5% 2 4 4 4 4 4 5% 7% 49%	2365
	11th to 20th	Day	14% 6% 1 4 2 3 3 2 4 6% 54%	2200
	21st to end	Day	16% 6% 2 5% 4 4 4 3 5% 7% 44%	2200
October	1st to 10th	Day	21% 4 2 6% 3 3 3 3 4 6% 44%	2200
	11th to 20th	Day	17% 4 2 5% 4 3 4 3 6% 7% 46%	1956
	21st to end	Day	20% 6% 2 5% 4 3 4 4 4 6% 42%	1980
November	1st to 10th	Day	15% 7% 2 5% 4 3 3 3 4 5% 48%	1851
	11th to 20th	Day	17% 7% 2 5% 3 2 3 3 4 6% 47%	1890
	21st to end	Day	19% 7% 2 5% 3 3 3 4 5% 7% 42%	1890
December	1st to 10th	Day	16% 8% 2 4 3 3 4 3 5% 5% 48%	2792
	11th to 20th	Day	20% 6% 2 5% 3 3 3 3 4 6% 46%	3066
	21st to end	Day	21% 10% 3 6% 4 3 5% 4 4 5% 36%	4048
January	1st to 10th	Night	15% 7% 2 5% 3 4 3 3 5% 7% 46%	8234
	11th to 20th	Night	16% 10% 3 8% 5% 4 4 3 5% 6% 36%	8235
	21st to end	Night	15% 9% 3 6% 5% 4 4 3 5% 5% 40%	9057
February	1st to 10th	Night	16% 10% 2 7% 5% 4 4 4 5% 6% 37%	2667
	11th to 20th	Night	15% 9% 3 6% 5% 4 4 4 5% 7% 39%	2458
	21st to end	Night	16% 9% 3 5% 4 3 3 3 4 6% 42%	2076
March	1st to 10th	Night	26% 9% 2 6% 4 3 3 3 4 5% 36%	5484
	11th to 20th	Night	14% 11% 4 7% 5% 4 4 3 4 6% 36%	5199
	21st to end	Night	27% 8% 3 6% 4 4 4 3 5% 5% 32%	5252
April	1st to 10th	Night	20% 9% 3 6% 4 4 4 4 4 6% 35%	2000
	11th to 20th	Night	19% 9% 2 5% 4 4 3 3 5% 6% 40%	1921
	21st to end	Night	19% 7% 2 7% 5% 6% 4 3 5% 5% 37%	1800
May	1st to 10th	Night	30% 11% 3 7% 4 3 4 3 4 6% 25%	4054
	11th to 20th	Night	17% 10% 3 7% 5% 5% 7% 5% 6% 8% 28%	4033
	21st to end	Night	20% 8% 4 8% 5% 4 5% 4 4 6% 31%	3953
June	1st to 10th	Night	20% 8% 3 6% 5% 4 4 3 4 6% 37%	1600
	11th to 20th	Night	17% 7% 3 6% 4 4 4 4 6% 9% 36%	1600
	21st to end	Night	17% 7% 2 6% 4 4 4 4 6% 7% 37%	1600
July	1st to 10th	Night	11% 7% 2 8% 5% 5% 5% 4 6% 10% 36%	3600
	11th to 20th	Night	9% 7% 3 7% 5% 5% 5% 5% 7% 10% 38%	3600
	21st to end	Night	12% 7% 2 7% 4 4 4 3 5% 7% 44%	3926
August	1st to 10th	Night	17% 7% 3 8% 5% 5% 5% 5% 6% 8% 33%	2898
	11th to 20th	Night	11% 8% 3 8% 5% 6% 5% 5% 7% 9% 33%	2872
	21st to end	Night	9% 5% 2 5% 3 4 4 4 6% 9% 50%	3538
September	1st to 10th	Night	11% 6% 1 6% 4 4 3 4 5% 7% 48%	2034
	11th to 20th	Night	14% 5% 1 5% 3 3 3 3 4 6% 53%	2200
	21st to end	Night	16% 5% 2 6% 4 4 4 3 6% 7% 43%	2200
October	1st to 10th	Night	19% 5% 2 6% 4 4 4 3 5% 6% 42%	2200
	11th to 20th	Night	16% 5% 2 6% 4 4 4 4 5% 7% 45%	2440
	21st to end	Night	21% 7% 3 6% 3 4 4 4 4 6% 39%	2860
November	1st to 10th	Night	15% 5% 2 6% 4 4 4 3 5% 6% 48%	2667
	11th to 20th	Night	16% 7% 2 5% 4 4 4 2 5% 6% 46%	2730
	21st to end	Night	16% 7% 3 5% 4 4 3 3 5% 6% 43%	2730
December	1st to 10th	Night	18% 8% 2 5% 4 4 4 3 4 5% 42%	4602
	11th to 20th	Night	20% 9% 2 5% 3 3 4 3 5% 5% 41%	5348
	21st to end	Night	19% 8% 3 7% 4 4 3 3 5% 6% 38%	7150

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	44% 3 9% 26% 16% 1	4662
	11th to 20th	Day	42% 3 10% 22% 20% 4	4680
	21st to end	Day	40% 2 9% 25% 21% 2	5124
February	1st to 10th	Day	47% 3 12% 20% 16% 2	1945
	11th to 20th	Day	44% 5% 10% 23% 15% 3	2057
	21st to end	Day	48% 3 10% 21% 14% 3	1730
March	1st to 10th	Day	51% 3 8% 15% 12% 10%	4579
	11th to 20th	Day	46% 3 13% 25% 12% 2	4914
	21st to end	Day	56% 2 5% 15% 14% 8%	5665
April	1st to 10th	Day	50% 3 9% 18% 17% 4	2400
	11th to 20th	Day	45% 4 10% 21% 16% 4	2427
	21st to end	Day	47% 4 7% 20% 18% 3	2600
May	1st to 10th	Day	61% 4 12% 15% 7% 1	5897
	11th to 20th	Day	53% 4 14% 17% 10% 2	5865
	21st to end	Day	47% 4 13% 21% 13% 1	6949
June	1st to 10th	Day	48% 5% 11% 22% 12% 1	2800
	11th to 20th	Day	43% 4 14% 21% 16% 3	2800
	21st to end	Day	45% 5% 13% 24% 13% 1	2800
July	1st to 10th	Day	47% 5% 12% 20% 14% 1	6290
	11th to 20th	Day	40% 4 16% 27% 13% 1	6285
	21st to end	Day	39% 4 12% 28% 15% 1	6711
August	1st to 10th	Day	45% 6% 16% 24% 9% 1	4222
	11th to 20th	Day	44% 5% 13% 27% 10% 1	4214
	21st to end	Day	32% 5% 13% 31% 18% 2	4355
September	1st to 10th	Day	36% 4 11% 26% 22% 1	2365
	11th to 20th	Day	36% 2 8% 28% 23% 2	2200
	21st to end	Day	41% 4 8% 24% 21% 2	2200
October	1st to 10th	Day	43% 3 9% 24% 19% 3	3590
	11th to 20th	Day	33% 2 7% 30% 24% 3	3159
	21st to end	Day	34% 3 9% 30% 21% 3	3180
November	1st to 10th	Day	40% 3 11% 27% 17% 2	1851
	11th to 20th	Day	40% 3 8% 22% 23% 3	1890
	21st to end	Day	43% 3 14% 23% 15% 2	1890
December	1st to 10th	Day	40% 2 14% 29% 14% 1	2792
	11th to 20th	Day	41% 2 12% 18% 20% 5%	3066
	21st to end	Day	50% 3 8% 21% 14% 5%	4048
January	1st to 10th	Night	40% 3 11% 29% 15% 2	8234
	11th to 20th	Night	49% 3 9% 19% 15% 4	8280
	21st to end	Night	46% 2 7% 20% 20% 4	9057
February	1st to 10th	Night	46% 4 12% 21% 15% 2	2667
	11th to 20th	Night	44% 4 10% 22% 16% 4	2460
	21st to end	Night	45% 3 8% 26% 15% 4	2076
March	1st to 10th	Night	51% 2 8% 16% 15% 8%	5494
	11th to 20th	Night	50% 3 14% 17% 13% 2	5200
	21st to end	Night	55% 3 5% 12% 20% 6%	5252
April	1st to 10th	Night	50% 3 10% 17% 16% 4	2000
	11th to 20th	Night	47% 3 8% 21% 19% 3	1921
	21st to end	Night	48% 4 10% 18% 18% 3	1800
May	1st to 10th	Night	62% 3 12% 13% 8% 2	4060
	11th to 20th	Night	53% 4 16% 15% 9% 1	4034
	21st to end	Night	54% 4 13% 18% 11% 1	3954
June	1st to 10th	Night	49% 4 12% 22% 13%	1600
	11th to 20th	Night	44% 5% 14% 21% 15% 2	1600
	21st to end	Night	43% 7% 13% 22% 14% 1	1600
July	1st to 10th	Night	44% 4 12% 22% 16%	3560
	11th to 20th	Night	42% 4 18% 20% 15% 1	3552
	21st to end	Night	39% 4 11% 31% 14% 1	3809
August	1st to 10th	Night	49% 6% 13% 20% 11% 1	2887
	11th to 20th	Night	46% 7% 14% 23% 11% 1	2899
	21st to end	Night	30% 4 15% 28% 23% 1	3538
September	1st to 10th	Night	37% 4 11% 27% 20% 1	2034
	11th to 20th	Night	35% 3 9% 25% 26% 2	2200
	21st to end	Night	41% 4 8% 25% 19% 2	2200
October	1st to 10th	Night	42% 3 13% 24% 16% 2	3590
	11th to 20th	Night	29% 2 10% 29% 27% 3	3976
	21st to end	Night	35% 3 11% 31% 19% 2	4610
November	1st to 10th	Night	38% 4 11% 24% 20% 4	2667
	11th to 20th	Night	40% 3 10% 23% 21% 3	2730
	21st to end	Night	41% 3 13% 26% 14% 2	2730
December	1st to 10th	Night	45% 3 11% 28% 13% 1	4602
	11th to 20th	Night	46% 3 13% 15% 21% 1	5348
	21st to end	Night	47% 3 7% 23% 17% 2	7150

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	26% 22% 31% 17% 4	220
	11th to 20th	Day	24% 29% 31% 13% 3	220
	21st to end	Day	24% 26% 35% 12% 3	242
February	1st to 10th	Day	28% 20% 37% 14% 2	450
	11th to 20th	Day	25% 24% 37% 12% 1	536
	21st to end	Day	23% 20% 37% 15% 4	446
March	1st to 10th	Day	26% 19% 36% 16% 3	540
	11th to 20th	Day	23% 25% 34% 14% 2 1	528
	21st to end	Day	28% 20% 33% 12% 5% 1	550
April	1st to 10th	Day	28% 24% 26% 17% 5% 1	500
	11th to 20th	Day	25% 20% 35% 16% 4	492
	21st to end	Day	25% 15% 37% 20% 3 1	500
May	1st to 10th	Day	30% 18% 31% 16% 4 1	503
	11th to 20th	Day	19% 13% 38% 24% 4 1	527
	21st to end	Day	19% 10% 34% 28% 8% 1	573
June	1st to 10th	Day	21% 9% 34% 25% 11% 1	530
	11th to 20th	Day	16% 11% 38% 26% 7% 2	530
	21st to end	Day	18% 9% 35% 28% 8% 2	530
July	1st to 10th	Day	18% 6% 29% 33% 12% 3	525
	11th to 20th	Day	13% 8% 29% 34% 14% 2	524
	21st to end	Day	12% 5% 32% 40% 11% 1	576
August	1st to 10th	Day	11% 6% 30% 36% 14% 3	526
	11th to 20th	Day	14% 7% 26% 33% 16% 4	519
	21st to end	Day	13% 8% 30% 31% 15% 4	583
September	1st to 10th	Day	17% 8% 30% 28% 14% 4	530
	11th to 20th	Day	17% 10% 28% 24% 13% 8%	530
	21st to end	Day	19% 8% 33% 24% 10% 5%	530
October	1st to 10th	Day	24% 12% 24% 24% 13% 3	530
	11th to 20th	Day	21% 16% 26% 24% 11% 2	447
	21st to end	Day	27% 12% 35% 16% 9% 1	462
November	1st to 10th	Day	18% 16% 35% 21% 8% 2	425
	11th to 20th	Day	24% 22% 32% 18% 4 1	430
	21st to end	Day	27% 20% 30% 17% 6% 1	430
December	1st to 10th	Day	23% 19% 38% 15% 4	293
	11th to 20th	Day	29% 22% 36% 10% 2	220
	21st to end	Day	24% 22% 31% 17% 5% 2	242
January	1st to 10th	Night	22% 20% 39% 17% 3	840
	11th to 20th	Night	27% 18% 36% 16% 2	840
	21st to end	Night	20% 19% 39% 18% 4	924
February	1st to 10th	Night	23% 18% 37% 21% 2	840
	11th to 20th	Night	23% 17% 42% 15% 2	823
	21st to end	Night	24% 17% 35% 20% 3	692
March	1st to 10th	Night	26% 17% 37% 18% 3	840
	11th to 20th	Night	23% 17% 37% 19% 4	829
	21st to end	Night	26% 15% 35% 19% 5%	880
April	1st to 10th	Night	26% 16% 33% 21% 4	800
	11th to 20th	Night	24% 15% 36% 20% 6%	737
	21st to end	Night	23% 13% 34% 26% 4 1	600
May	1st to 10th	Night	28% 10% 34% 23% 5% 1	600
	11th to 20th	Night	21% 10% 37% 24% 6% 1	592
	21st to end	Night	23% 6% 31% 30% 10%	447
June	1st to 10th	Night	23% 5% 32% 30% 9% 2	400
	11th to 20th	Night	20% 7% 30% 35% 9% 1	400
	21st to end	Night	20% 5% 28% 37% 10%	400
July	1st to 10th	Night	17% 3 26% 42% 11% 2	390
	11th to 20th	Night	14% 6% 22% 40% 16% 1	388
	21st to end	Night	15% 3 27% 43% 12%	438
August	1st to 10th	Night	12% 3 24% 45% 16% 1	581
	11th to 20th	Night	14% 4 26% 39% 17% 1	592
	21st to end	Night	15% 3 25% 36% 19% 2	845
September	1st to 10th	Night	14% 4 28% 35% 17% 1	800
	11th to 20th	Night	16% 6% 25% 29% 19% 4	800
	21st to end	Night	19% 5% 27% 31% 16% 2	800
October	1st to 10th	Night	23% 8% 26% 27% 14% 2	800
	11th to 20th	Night	19% 11% 30% 27% 12% 1	800
	21st to end	Night	25% 13% 33% 23% 7%	880
November	1st to 10th	Night	17% 12% 36% 25% 8% 1	820
	11th to 20th	Night	21% 18% 34% 20% 6%	840
	21st to end	Night	22% 20% 34% 18% 5%	840
December	1st to 10th	Night	25% 17% 39% 16% 4	840
	11th to 20th	Night	23% 19% 35% 20% 3	840
	21st to end	Night	26% 16% 38% 18% 2	924

Page generated at 2026-03-15 02:23:53. Version ac07

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