Predator Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Predator Bay clear sky chart from 2005-11-06 to 2026-08-15.

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	8% 8% 3 8% 5% 5% 5% 4 7% 9% 40%	148498
	Night	6% 9% 3 9% 5% 5% 5% 4 6% 8% 39%	142121
Transparency	Day	39% 6% 14% 26% 12% 2	148200
	Night	41% 6% 15% 24% 12% 2	142003
Seeing	Day	12% 9% 26% 31% 17% 5%	17699
	Night	11% 6% 29% 37% 15% 2	26672

By Month

Percentage Cloud Cover NW (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	2 9% 7% 13% 8% 8% 5% 4 7% 9% 29%	4125
	11th to 20th	Day	2 7% 3 10% 6% 5% 5% 4 7% 7% 44%	4238
	21st to end	Day	2 6% 3 9% 5% 4 4 4 7% 11% 45%	5186
February	1st to 10th	Day	3 11% 5% 12% 6% 7% 6% 5% 7% 7% 30%	1680
	11th to 20th	Day	4 12% 5% 11% 6% 6% 6% 5% 7% 9% 29%	1844
	21st to end	Day	3 12% 6% 9% 6% 6% 6% 4 7% 9% 33%	1686
March	1st to 10th	Day	3 9% 4 11% 6% 5% 5% 3 5% 11% 38%	4618
	11th to 20th	Day	4 10% 5% 8% 5% 5% 4 5% 6% 8% 40%	5059
	21st to end	Day	7% 20% 7% 12% 5% 4 5% 5% 6% 7% 22%	5685
April	1st to 10th	Day	8% 15% 4 10% 6% 5% 5% 4 6% 8% 29%	2578
	11th to 20th	Day	11% 13% 4 9% 5% 5% 4 5% 6% 8% 30%	2700
	21st to end	Day	11% 12% 4 7% 6% 4 5% 4 6% 8% 32%	2730
May	1st to 10th	Day	12% 9% 3 6% 4 4 5% 4 7% 8% 38%	7979
	11th to 20th	Day	11% 10% 4 9% 6% 6% 6% 5% 8% 9% 26%	8755
	21st to end	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 9% 35%	9649
June	1st to 10th	Day	16% 7% 3 8% 6% 5% 5% 5% 7% 9% 31%	3150
	11th to 20th	Day	19% 9% 2 7% 5% 5% 6% 5% 7% 8% 28%	3150
	21st to end	Day	9% 4 2 5% 5% 4 6% 5% 9% 10% 41%	3150
July	1st to 10th	Day	6% 4 2 5% 4 4 5% 4 6% 9% 52%	8820
	11th to 20th	Day	8% 4 1 5% 3 4 4 4 7% 9% 50%	8820
	21st to end	Day	6% 4 2 4 3 3 3 3 5% 8% 58%	9317
August	1st to 10th	Day	8% 6% 3 6% 4 4 5% 5% 8% 10% 43%	4681
	11th to 20th	Day	7% 5% 2 5% 4 5% 4 4 8% 11% 45%	4244
	21st to end	Day	9% 4 1 4 3 3 4 4 6% 8% 54%	4664
September	1st to 10th	Day	10% 5% 2 6% 3 3 4 3 5% 6% 52%	2475
	11th to 20th	Day	13% 7% 2 6% 4 4 3 4 5% 7% 46%	2200
	21st to end	Day	8% 7% 3 6% 4 4 4 4 6% 8% 46%	2200
October	1st to 10th	Day	7% 7% 2 7% 4 4 5% 4 7% 9% 44%	3450
	11th to 20th	Day	6% 7% 3 6% 4 4 5% 5% 8% 10% 44%	3011
	21st to end	Day	6% 7% 3 7% 5% 4 5% 4 6% 7% 45%	3200
November	1st to 10th	Day	8% 14% 4 9% 5% 4 5% 4 5% 8% 34%	1725
	11th to 20th	Day	7% 12% 3 7% 5% 5% 4 3 7% 7% 40%	1612
	21st to end	Day	4 12% 4 10% 4 6% 4 5% 6% 10% 34%	1470
December	1st to 10th	Day	3 12% 5% 11% 6% 6% 6% 4 6% 8% 34%	2360
	11th to 20th	Day	2 10% 5% 11% 7% 7% 6% 5% 6% 8% 32%	2712
	21st to end	Day	3 10% 4 9% 5% 4 5% 4 6% 8% 42%	3575
January	1st to 10th	Night	4 12% 5% 12% 8% 7% 6% 4 6% 8% 29%	8768
	11th to 20th	Night	2 7% 4 11% 6% 5% 5% 5% 6% 8% 39%	8719
	21st to end	Night	2 8% 4 10% 7% 5% 5% 4 6% 8% 41%	8994
February	1st to 10th	Night	4 11% 5% 11% 6% 6% 7% 5% 7% 8% 31%	2940
	11th to 20th	Night	5% 12% 5% 11% 6% 6% 6% 5% 7% 8% 30%	2662
	21st to end	Night	3 10% 4 13% 7% 6% 5% 4 6% 7% 34%	2118
March	1st to 10th	Night	2 8% 4 11% 7% 6% 6% 5% 6% 10% 34%	5496
	11th to 20th	Night	4 9% 4 10% 6% 5% 5% 5% 6% 8% 39%	5160
	21st to end	Night	8% 20% 6% 12% 6% 5% 4 4 6% 7% 23%	5529
April	1st to 10th	Night	9% 14% 5% 9% 6% 4 6% 3 6% 7% 31%	2042
	11th to 20th	Night	11% 11% 4 9% 6% 5% 5% 4 6% 7% 32%	1871
	21st to end	Night	10% 11% 3 8% 5% 5% 6% 5% 6% 8% 33%	1890
May	1st to 10th	Night	13% 10% 3 8% 4 4 5% 4 4 7% 40%	4953
	11th to 20th	Night	11% 10% 3 9% 5% 5% 5% 4 7% 11% 30%	4105
	21st to end	Night	10% 7% 3 7% 5% 5% 6% 5% 8% 9% 35%	4522
June	1st to 10th	Night	14% 8% 3 8% 6% 4 6% 4 7% 7% 33%	1470
	11th to 20th	Night	17% 7% 3 8% 4 4 5% 5% 6% 8% 32%	1470
	21st to end	Night	8% 4 1 5% 4 5% 6% 4 8% 10% 44%	1470
July	1st to 10th	Night	6% 5% 2 7% 4 4 4 4 5% 7% 52%	4140
	11th to 20th	Night	6% 5% 2 4 3 4 4 4 7% 9% 53%	4140
	21st to end	Night	8% 4 2 5% 3 3 3 2 4 7% 59%	4735
August	1st to 10th	Night	10% 6% 2 7% 5% 4 5% 4 7% 8% 43%	2689
	11th to 20th	Night	6% 5% 2 6% 4 4 5% 5% 8% 10% 43%	2902
	21st to end	Night	8% 4 1 5% 2 3 4 3 6% 9% 55%	3245
September	1st to 10th	Night	9% 6% 2 6% 3 3 3 2 6% 8% 51%	1923
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 5% 7% 50%	2200
	21st to end	Night	9% 6% 2 5% 3 4 4 3 6% 8% 49%	2200
October	1st to 10th	Night	7% 6% 1 6% 4 4 4 3 6% 8% 51%	3745
	11th to 20th	Night	6% 6% 2 5% 4 4 5% 4 6% 9% 49%	4135
	21st to end	Night	5% 8% 3 7% 5% 5% 5% 4 7% 7% 45%	4600
November	1st to 10th	Night	7% 14% 4 8% 5% 5% 5% 4 6% 7% 36%	2772
	11th to 20th	Night	4 10% 4 9% 6% 5% 5% 5% 6% 8% 39%	3003
	21st to end	Night	4 11% 4 9% 5% 5% 5% 4 6% 9% 38%	3150
December	1st to 10th	Night	3 10% 4 10% 6% 6% 7% 6% 7% 9% 33%	5040
	11th to 20th	Night	2 10% 4 13% 8% 6% 6% 5% 7% 9% 30%	5700
	21st to end	Night	4 10% 5% 8% 5% 4 5% 4 6% 8% 40%	7623

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	51% 4 10% 21% 12% 2	4125
	11th to 20th	Day	38% 4 15% 22% 17% 3	4259
	21st to end	Day	33% 6% 15% 31% 14% 1	5187
February	1st to 10th	Day	50% 8% 14% 15% 11% 2	1680
	11th to 20th	Day	49% 6% 13% 20% 11% 2	1853
	21st to end	Day	47% 6% 14% 21% 12% 1	1686
March	1st to 10th	Day	41% 4 15% 23% 16% 1	4618
	11th to 20th	Day	39% 5% 13% 25% 16% 1	5060
	21st to end	Day	60% 6% 12% 15% 6%	5685
April	1st to 10th	Day	51% 5% 15% 19% 8% 1	2578
	11th to 20th	Day	49% 6% 13% 21% 10% 1	2700
	21st to end	Day	48% 7% 13% 21% 10% 1	2730
May	1st to 10th	Day	42% 5% 9% 27% 13% 3	7979
	11th to 20th	Day	49% 7% 11% 23% 8% 2	8759
	21st to end	Day	42% 6% 16% 26% 10% 1	9650
June	1st to 10th	Day	48% 7% 14% 20% 9% 2	3150
	11th to 20th	Day	51% 8% 13% 19% 7% 2	3150
	21st to end	Day	34% 9% 19% 26% 10% 2	3150
July	1st to 10th	Day	27% 7% 16% 31% 16% 3	8746
	11th to 20th	Day	29% 6% 18% 28% 14% 5%	8739
	21st to end	Day	24% 5% 13% 27% 21% 9%	9114
August	1st to 10th	Day	33% 8% 15% 36% 7% 1	4664
	11th to 20th	Day	31% 7% 24% 30% 7% 1	4283
	21st to end	Day	27% 6% 17% 36% 14% 1	4663
September	1st to 10th	Day	31% 7% 14% 27% 15% 5%	2475
	11th to 20th	Day	38% 5% 13% 29% 13% 2	2200
	21st to end	Day	35% 6% 14% 29% 12% 3	2200
October	1st to 10th	Day	36% 5% 16% 34% 8% 1	3450
	11th to 20th	Day	33% 6% 19% 26% 13% 3	3011
	21st to end	Day	37% 5% 10% 33% 13% 2	3200
November	1st to 10th	Day	49% 7% 11% 20% 11% 2	1725
	11th to 20th	Day	42% 5% 16% 25% 10% 1	1612
	21st to end	Day	44% 7% 15% 24% 8% 2	1470
December	1st to 10th	Day	48% 5% 14% 24% 8% 2	2360
	11th to 20th	Day	48% 6% 19% 20% 7% 1	2714
	21st to end	Day	39% 5% 11% 24% 18% 3	3575
January	1st to 10th	Night	53% 5% 11% 20% 10% 2	8769
	11th to 20th	Night	42% 4 16% 21% 13% 5%	8760
	21st to end	Night	40% 5% 16% 26% 12% 1	8994
February	1st to 10th	Night	49% 6% 12% 19% 12% 2	2940
	11th to 20th	Night	49% 6% 12% 20% 12% 1	2663
	21st to end	Night	47% 5% 12% 22% 11% 3	2118
March	1st to 10th	Night	43% 6% 18% 20% 12% 2	5496
	11th to 20th	Night	42% 6% 14% 23% 14% 1	5160
	21st to end	Night	60% 6% 11% 13% 9% 1	5529
April	1st to 10th	Night	51% 6% 12% 20% 11% 1	2042
	11th to 20th	Night	50% 6% 12% 22% 9% 1	1871
	21st to end	Night	47% 8% 13% 21% 9% 2	1890
May	1st to 10th	Night	45% 6% 10% 24% 15% 1	4950
	11th to 20th	Night	46% 7% 13% 26% 8% 1	4105
	21st to end	Night	42% 7% 16% 27% 7% 1	4526
June	1st to 10th	Night	47% 7% 14% 21% 11% 1	1470
	11th to 20th	Night	46% 9% 14% 21% 9% 2	1470
	21st to end	Night	33% 10% 20% 26% 10% 1	1470
July	1st to 10th	Night	30% 6% 17% 29% 17% 1	4105
	11th to 20th	Night	27% 7% 18% 32% 11% 5%	4098
	21st to end	Night	26% 4 14% 28% 18% 9%	4634
August	1st to 10th	Night	37% 7% 14% 28% 13% 1	2681
	11th to 20th	Night	31% 10% 23% 26% 9% 1	2929
	21st to end	Night	25% 5% 18% 35% 14% 2	3245
September	1st to 10th	Night	32% 6% 15% 27% 15% 5%	1923
	11th to 20th	Night	34% 6% 14% 28% 14% 4	2200
	21st to end	Night	32% 5% 18% 27% 15% 4	2200
October	1st to 10th	Night	31% 5% 15% 29% 18% 2	3745
	11th to 20th	Night	32% 6% 19% 24% 18% 2	4135
	21st to end	Night	37% 5% 11% 32% 14% 1	4600
November	1st to 10th	Night	47% 6% 12% 21% 12% 2	2772
	11th to 20th	Night	42% 7% 15% 22% 13% 1	3003
	21st to end	Night	41% 6% 17% 23% 9% 3	3150
December	1st to 10th	Night	47% 7% 17% 20% 7% 2	5040
	11th to 20th	Night	49% 7% 19% 18% 7%	5697
	21st to end	Night	41% 4 10% 26% 16% 3	7623

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	4 10% 24% 37% 16% 10%	220
	11th to 20th	Day	10% 6% 29% 35% 15% 5%	220
	21st to end	Day	7% 10% 20% 43% 18% 3	242
February	1st to 10th	Day	9% 10% 29% 35% 14% 3	220
	11th to 20th	Day	7% 6% 32% 37% 17% 2	330
	21st to end	Day	8% 9% 29% 35% 16% 2	402
March	1st to 10th	Day	8% 12% 34% 29% 13% 4	540
	11th to 20th	Day	9% 11% 29% 32% 14% 4	540
	21st to end	Day	12% 18% 30% 25% 10% 5%	594
April	1st to 10th	Day	13% 13% 35% 24% 12% 3	540
	11th to 20th	Day	16% 14% 26% 29% 12% 4	532
	21st to end	Day	14% 17% 27% 25% 13% 3	540
May	1st to 10th	Day	18% 10% 25% 25% 16% 6%	580
	11th to 20th	Day	17% 7% 23% 28% 18% 6%	775
	21st to end	Day	17% 7% 20% 29% 20% 6%	844
June	1st to 10th	Day	16% 10% 25% 31% 15% 4	780
	11th to 20th	Day	20% 10% 26% 29% 13% 2	780
	21st to end	Day	12% 6% 23% 33% 20% 6%	780
July	1st to 10th	Day	9% 5% 22% 32% 25% 6%	771
	11th to 20th	Day	11% 7% 22% 34% 22% 4	768
	21st to end	Day	6% 8% 25% 34% 21% 6%	763
August	1st to 10th	Day	11% 6% 25% 31% 20% 7%	567
	11th to 20th	Day	10% 5% 22% 33% 23% 7%	534
	21st to end	Day	11% 7% 22% 30% 20% 10%	583
September	1st to 10th	Day	11% 7% 25% 30% 20% 8%	530
	11th to 20th	Day	17% 6% 23% 30% 18% 7%	530
	21st to end	Day	11% 14% 29% 30% 11% 4	530
October	1st to 10th	Day	13% 7% 25% 31% 20% 4	445
	11th to 20th	Day	12% 10% 30% 28% 15% 4	330
	21st to end	Day	13% 12% 35% 25% 12% 3	363
November	1st to 10th	Day	18% 8% 28% 32% 11% 3	330
	11th to 20th	Day	12% 10% 35% 29% 10% 4	294
	21st to end	Day	6% 10% 30% 31% 15% 9%	220
December	1st to 10th	Day	7% 7% 27% 40% 14% 5%	220
	11th to 20th	Day	6% 12% 32% 35% 11% 3	220
	21st to end	Day	8% 6% 21% 39% 21% 5%	242
January	1st to 10th	Night	9% 9% 32% 37% 11% 2	1050
	11th to 20th	Night	8% 7% 35% 36% 12% 1	1029
	21st to end	Night	9% 10% 33% 37% 10% 2	924
February	1st to 10th	Night	8% 7% 32% 34% 15% 3	840
	11th to 20th	Night	10% 5% 32% 39% 12% 1	824
	21st to end	Night	8% 6% 29% 36% 18% 3	692
March	1st to 10th	Night	8% 6% 33% 36% 14% 4	840
	11th to 20th	Night	9% 8% 33% 36% 12% 2	840
	21st to end	Night	13% 6% 31% 35% 13% 2	924
April	1st to 10th	Night	14% 8% 30% 33% 13% 2	782
	11th to 20th	Night	17% 8% 30% 34% 11%	623
	21st to end	Night	17% 8% 28% 33% 13%	630
May	1st to 10th	Night	17% 9% 25% 34% 16% 1	541
	11th to 20th	Night	14% 8% 24% 34% 20%	414
	21st to end	Night	20% 5% 21% 34% 19%	455
June	1st to 10th	Night	16% 7% 26% 35% 14% 1	420
	11th to 20th	Night	20% 3 26% 37% 14%	420
	21st to end	Night	10% 5% 18% 41% 25% 1	420
July	1st to 10th	Night	10% 4 17% 43% 25% 1	410
	11th to 20th	Night	10% 2 21% 43% 21% 2	408
	21st to end	Night	7% 4 20% 45% 23% 2	460
August	1st to 10th	Night	11% 5% 13% 38% 32% 2	418
	11th to 20th	Night	10% 4 17% 46% 22% 2	583
	21st to end	Night	9% 3 21% 42% 23% 1	660
September	1st to 10th	Night	12% 4 21% 38% 22% 3	703
	11th to 20th	Night	16% 4 18% 39% 21% 2	800
	21st to end	Night	13% 4 31% 36% 14% 2	800
October	1st to 10th	Night	14% 4 26% 38% 16% 2	800
	11th to 20th	Night	12% 5% 30% 36% 14% 3	800
	21st to end	Night	11% 7% 34% 35% 12% 1	880
November	1st to 10th	Night	14% 9% 36% 31% 9% 1	927
	11th to 20th	Night	10% 10% 39% 31% 9% 1	1050
	21st to end	Night	9% 7% 35% 37% 11% 2	1050
December	1st to 10th	Night	9% 6% 34% 36% 13% 2	1050
	11th to 20th	Night	7% 6% 38% 39% 10% 1	1050
	21st to end	Night	9% 6% 32% 39% 12% 3	1155

Page generated at 2026-08-12 00:37:13. Version ac07

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