Buckley
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Buckley clear sky chart from 2005-11-06 to 2025-07-06.

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	20% 10% 3 8% 5% 4 4 4 5% 6% 31%	124749
	Night	22% 11% 3 7% 5% 4 4 3 5% 6% 30%	122763
Transparency	Day	53% 8% 12% 16% 9% 2	124511
	Night	55% 8% 11% 16% 9% 2	122645
Seeing	Day	25% 14% 23% 25% 11% 3	15751
	Night	29% 11% 17% 25% 16% 2	24179

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	36% 15% 3 9% 5% 5% 4 3 5% 6% 10%	3639
	11th to 20th	Day	17% 11% 3 8% 5% 5% 5% 4 5% 7% 30%	3616
	21st to end	Day	28% 10% 3 7% 4 3 3 2 4 4 31%	4124
February	1st to 10th	Day	29% 12% 4 8% 6% 4 5% 3 4 6% 18%	1800
	11th to 20th	Day	31% 14% 4 7% 5% 4 4 3 4 4 19%	1755
	21st to end	Day	29% 17% 4 7% 5% 4 4 3 3 4 19%	1570
March	1st to 10th	Day	16% 13% 4 10% 7% 6% 7% 5% 7% 7% 20%	4601
	11th to 20th	Day	19% 16% 4 11% 6% 5% 4 3 3 3 26%	5000
	21st to end	Day	25% 14% 4 10% 6% 6% 5% 5% 6% 7% 12%	5695
April	1st to 10th	Day	26% 15% 3 8% 5% 6% 6% 5% 6% 5% 14%	2400
	11th to 20th	Day	22% 14% 3 8% 6% 4 5% 4 5% 6% 24%	2372
	21st to end	Day	24% 14% 3 10% 6% 5% 4 3 4 5% 21%	2641
May	1st to 10th	Day	17% 9% 3 7% 5% 5% 5% 4 5% 6% 35%	6320
	11th to 20th	Day	19% 12% 4 10% 6% 5% 5% 4 6% 6% 23%	6277
	21st to end	Day	22% 10% 3 8% 5% 4 5% 4 5% 7% 27%	6903
June	1st to 10th	Day	24% 10% 3 7% 5% 5% 4 3 5% 6% 27%	2800
	11th to 20th	Day	25% 11% 4 9% 6% 5% 6% 4 5% 6% 19%	2947
	21st to end	Day	15% 8% 3 6% 5% 5% 5% 4 6% 7% 37%	3000
July	1st to 10th	Day	8% 4 2 5% 2 2 3 3 4 6% 61%	4784
	11th to 20th	Day	7% 4 1 3 3 2 2 2 4 5% 66%	4420
	21st to end	Day	12% 5% 2 4 3 3 3 3 5% 6% 55%	4790
August	1st to 10th	Day	6% 4 1 4 3 3 3 3 5% 7% 60%	4320
	11th to 20th	Day	10% 8% 3 8% 5% 5% 5% 4 6% 7% 39%	4026
	21st to end	Day	16% 8% 3 6% 4 4 4 3 4 6% 42%	4304
September	1st to 10th	Day	12% 6% 2 4 3 3 4 4 4 7% 51%	2280
	11th to 20th	Day	15% 7% 2 8% 4 5% 4 4 6% 7% 38%	2280
	21st to end	Day	18% 6% 3 7% 5% 4 4 3 5% 5% 40%	2015
October	1st to 10th	Day	18% 7% 2 5% 4 3 3 3 5% 9% 40%	3180
	11th to 20th	Day	25% 8% 3 7% 5% 4 4 3 5% 6% 27%	3161
	21st to end	Day	26% 9% 4 9% 6% 5% 5% 4 4 5% 22%	3241
November	1st to 10th	Day	32% 11% 3 7% 5% 5% 4 4 5% 6% 18%	1639
	11th to 20th	Day	32% 13% 3 7% 4 4 5% 3 5% 4 20%	1600
	21st to end	Day	29% 12% 3 8% 4 4 5% 3 5% 6% 21%	1600
December	1st to 10th	Day	23% 10% 2 6% 4 5% 4 4 4 6% 34%	2620
	11th to 20th	Day	30% 11% 5% 9% 6% 5% 5% 4 5% 5% 16%	3025
	21st to end	Day	30% 14% 4 10% 6% 5% 5% 4 4 4 14%	4004
January	1st to 10th	Night	32% 17% 4 10% 5% 5% 4 3 5% 4 12%	6306
	11th to 20th	Night	20% 12% 4 7% 4 4 4 4 5% 7% 31%	6282
	21st to end	Night	26% 9% 4 7% 4 4 4 3 4 5% 31%	6823
February	1st to 10th	Night	29% 14% 3 9% 6% 5% 4 3 4 5% 17%	2600
	11th to 20th	Night	28% 14% 3 7% 6% 4 4 3 3 5% 24%	2532
	21st to end	Night	27% 15% 3 7% 4 5% 5% 4 5% 5% 20%	2059
March	1st to 10th	Night	18% 13% 4 9% 6% 5% 5% 4 6% 7% 21%	5290
	11th to 20th	Night	21% 12% 4 8% 5% 5% 4 3 4 6% 28%	4999
	21st to end	Night	28% 15% 4 9% 6% 5% 5% 4 6% 5% 13%	5280
April	1st to 10th	Night	25% 13% 3 8% 6% 5% 5% 5% 5% 6% 18%	2000
	11th to 20th	Night	22% 11% 3 7% 6% 5% 4 4 5% 6% 28%	1979
	21st to end	Night	25% 11% 3 8% 5% 5% 5% 4 5% 7% 23%	1754
May	1st to 10th	Night	20% 10% 3 6% 4 4 3 3 4 4 41%	3640
	11th to 20th	Night	22% 11% 3 8% 6% 5% 5% 4 5% 7% 24%	3616
	21st to end	Night	19% 12% 3 9% 5% 6% 5% 4 5% 7% 25%	3972
June	1st to 10th	Night	21% 10% 3 8% 5% 4 4 3 5% 7% 30%	1600
	11th to 20th	Night	19% 12% 3 9% 5% 4 4 4 4 7% 27%	1447
	21st to end	Night	16% 7% 3 6% 4 4 3 3 5% 7% 42%	1400
July	1st to 10th	Night	8% 5% 2 5% 3 3 3 2 4 5% 60%	2282
	11th to 20th	Night	6% 4 1 3 2 2 2 2 2 4 71%	2540
	21st to end	Night	13% 4 1 3 3 2 3 3 4 6% 59%	2762
August	1st to 10th	Night	6% 3 1 3 2 2 2 3 4 6% 68%	2610
	11th to 20th	Night	14% 7% 3 6% 4 4 4 3 4 6% 45%	2812
	21st to end	Night	17% 7% 2 5% 3 4 4 2 3 5% 48%	3369
September	1st to 10th	Night	12% 5% 2 4 3 3 3 4 5% 7% 53%	1900
	11th to 20th	Night	17% 8% 3 8% 4 3 3 4 4 5% 40%	1900
	21st to end	Night	17% 6% 2 6% 5% 4 4 4 4 7% 42%	2161
October	1st to 10th	Night	18% 5% 2 6% 4 4 4 3 5% 8% 42%	3800
	11th to 20th	Night	26% 8% 3 6% 3 4 4 4 4 6% 31%	3777
	21st to end	Night	26% 10% 4 8% 5% 4 4 3 5% 7% 24%	4320
November	1st to 10th	Night	34% 8% 3 7% 5% 5% 4 4 5% 5% 20%	2659
	11th to 20th	Night	31% 12% 3 8% 5% 4 4 3 4 4 21%	2800
	21st to end	Night	28% 12% 4 8% 5% 3 4 4 5% 5% 22%	2800
December	1st to 10th	Night	20% 10% 2 7% 5% 4 4 3 5% 6% 33%	4560
	11th to 20th	Night	30% 15% 4 10% 6% 4 4 3 4 4 15%	5180
	21st to end	Night	27% 14% 5% 11% 6% 5% 5% 4 4 5% 13%	6952

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	74% 7% 6% 9% 4	3639
	11th to 20th	Day	52% 8% 11% 18% 9% 1	3640
	21st to end	Day	55% 7% 6% 17% 14% 1	4124
February	1st to 10th	Day	68% 8% 10% 9% 5% 1	1800
	11th to 20th	Day	68% 8% 7% 9% 6% 2	1764
	21st to end	Day	71% 7% 7% 11% 4	1570
March	1st to 10th	Day	58% 10% 16% 11% 6%	4601
	11th to 20th	Day	63% 7% 8% 20% 2	5000
	21st to end	Day	70% 11% 11% 7% 1	5695
April	1st to 10th	Day	71% 10% 11% 7% 1	2400
	11th to 20th	Day	62% 8% 11% 12% 6% 1	2372
	21st to end	Day	68% 8% 11% 10% 3 1	2641
May	1st to 10th	Day	48% 8% 15% 21% 8%	6320
	11th to 20th	Day	57% 14% 15% 12% 2	6280
	21st to end	Day	56% 11% 19% 12% 2	6904
June	1st to 10th	Day	58% 10% 14% 13% 5%	2800
	11th to 20th	Day	66% 10% 11% 10% 2	2947
	21st to end	Day	46% 10% 17% 17% 8% 1	3000
July	1st to 10th	Day	26% 6% 10% 19% 20% 19%	4711
	11th to 20th	Day	21% 5% 8% 24% 36% 6%	4345
	21st to end	Day	29% 6% 13% 33% 17% 3	4639
August	1st to 10th	Day	23% 6% 12% 35% 22% 3	4303
	11th to 20th	Day	42% 10% 16% 22% 9% 1	4065
	21st to end	Day	43% 7% 13% 22% 14% 1	4303
September	1st to 10th	Day	32% 8% 17% 24% 15% 5%	2280
	11th to 20th	Day	45% 10% 12% 16% 14% 3	2280
	21st to end	Day	45% 8% 16% 17% 12% 2	2015
October	1st to 10th	Day	41% 7% 12% 30% 10% 1	3180
	11th to 20th	Day	55% 7% 12% 16% 8% 1	3161
	21st to end	Day	61% 8% 11% 10% 8% 2	3241
November	1st to 10th	Day	67% 8% 11% 10% 4 1	1639
	11th to 20th	Day	70% 7% 8% 7% 7% 2	1600
	21st to end	Day	64% 8% 7% 10% 9% 2	1600
December	1st to 10th	Day	52% 6% 8% 17% 15% 2	2620
	11th to 20th	Day	68% 9% 10% 9% 3	3028
	21st to end	Day	72% 8% 9% 8% 2	4004
January	1st to 10th	Night	75% 6% 6% 8% 4 1	6306
	11th to 20th	Night	51% 8% 10% 20% 10% 1	6320
	21st to end	Night	54% 8% 8% 16% 13% 1	6823
February	1st to 10th	Night	68% 8% 8% 9% 6% 1	2600
	11th to 20th	Night	63% 8% 9% 10% 7% 3	2534
	21st to end	Night	67% 8% 9% 11% 4	2059
March	1st to 10th	Night	56% 10% 13% 13% 7%	5290
	11th to 20th	Night	56% 8% 14% 20% 2 1	5000
	21st to end	Night	67% 11% 12% 9%	5280
April	1st to 10th	Night	66% 11% 13% 9% 1	2000
	11th to 20th	Night	57% 10% 12% 14% 7% 1	1979
	21st to end	Night	64% 10% 10% 10% 5% 1	1754
May	1st to 10th	Night	47% 6% 13% 24% 9%	3637
	11th to 20th	Night	55% 12% 17% 12% 2	3616
	21st to end	Night	58% 12% 16% 13% 1	3972
June	1st to 10th	Night	55% 9% 14% 15% 6%	1600
	11th to 20th	Night	57% 9% 17% 14% 3	1447
	21st to end	Night	44% 9% 17% 20% 9% 2	1400
July	1st to 10th	Night	27% 7% 10% 18% 15% 24%	2247
	11th to 20th	Night	20% 4 7% 24% 40% 5%	2492
	21st to end	Night	28% 6% 13% 28% 20% 5%	2674
August	1st to 10th	Night	18% 5% 10% 39% 25% 3	2602
	11th to 20th	Night	41% 10% 17% 19% 10% 3	2839
	21st to end	Night	41% 6% 13% 24% 15% 1	3369
September	1st to 10th	Night	33% 8% 13% 24% 17% 5%	1900
	11th to 20th	Night	46% 9% 9% 17% 14% 5%	1900
	21st to end	Night	42% 10% 14% 18% 13% 4	2161
October	1st to 10th	Night	40% 7% 14% 28% 10% 1	3800
	11th to 20th	Night	54% 6% 12% 18% 10% 1	3777
	21st to end	Night	59% 8% 10% 13% 10%	4320
November	1st to 10th	Night	66% 8% 10% 11% 4 1	2659
	11th to 20th	Night	67% 7% 8% 9% 6% 2	2800
	21st to end	Night	65% 7% 7% 9% 10% 2	2800
December	1st to 10th	Night	51% 7% 9% 16% 15% 1	4560
	11th to 20th	Night	71% 8% 8% 9% 4	5176
	21st to end	Night	69% 11% 10% 7% 3	6952

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	39% 18% 19% 13% 9% 3	200
	11th to 20th	Day	30% 19% 20% 20% 10% 2	200
	21st to end	Day	35% 17% 16% 17% 11% 2	275
February	1st to 10th	Day	39% 14% 23% 16% 7% 1	400
	11th to 20th	Day	42% 16% 21% 15% 5% 1	395
	21st to end	Day	37% 18% 22% 17% 4 1	374
March	1st to 10th	Day	29% 21% 26% 18% 5%	500
	11th to 20th	Day	29% 20% 23% 19% 7% 1	500
	21st to end	Day	34% 20% 23% 17% 6%	550
April	1st to 10th	Day	35% 18% 22% 17% 7% 1	500
	11th to 20th	Day	27% 23% 27% 14% 7% 2	492
	21st to end	Day	26% 19% 27% 19% 7% 2	500
May	1st to 10th	Day	20% 17% 27% 26% 8% 2	503
	11th to 20th	Day	31% 13% 25% 20% 9% 3	528
	21st to end	Day	28% 14% 23% 22% 10% 2	573
June	1st to 10th	Day	26% 12% 22% 24% 13% 3	530
	11th to 20th	Day	26% 17% 28% 19% 8% 2	677
	21st to end	Day	18% 10% 22% 33% 15% 2	730
July	1st to 10th	Day	13% 8% 24% 40% 14% 2	679
	11th to 20th	Day	11% 7% 25% 37% 17% 4	484
	21st to end	Day	11% 5% 23% 38% 21% 4	531
August	1st to 10th	Day	10% 7% 17% 41% 17% 7%	487
	11th to 20th	Day	8% 5% 19% 42% 20% 6%	477
	21st to end	Day	12% 12% 25% 33% 13% 5%	539
September	1st to 10th	Day	15% 8% 24% 38% 12% 4	490
	11th to 20th	Day	18% 12% 23% 29% 15% 3	490
	21st to end	Day	18% 15% 23% 27% 16% 2	490
October	1st to 10th	Day	26% 11% 22% 22% 17% 2	490
	11th to 20th	Day	30% 14% 19% 20% 13% 4	490
	21st to end	Day	30% 18% 21% 20% 6% 4	420
November	1st to 10th	Day	40% 14% 15% 19% 11%	237
	11th to 20th	Day	39% 19% 16% 11% 12% 4	200
	21st to end	Day	33% 14% 22% 16% 12% 5%	200
December	1st to 10th	Day	40% 14% 16% 11% 14% 7%	200
	11th to 20th	Day	39% 15% 24% 17% 7% 1	200
	21st to end	Day	42% 14% 18% 17% 8%	220
January	1st to 10th	Night	42% 15% 19% 17% 6% 1	800
	11th to 20th	Night	33% 14% 20% 23% 10% 1	800
	21st to end	Night	32% 12% 19% 27% 9% 1	880
February	1st to 10th	Night	37% 12% 21% 23% 7% 1	800
	11th to 20th	Night	34% 13% 17% 26% 9%	784
	21st to end	Night	36% 15% 21% 21% 6% 1	660
March	1st to 10th	Night	29% 16% 19% 24% 11% 1	800
	11th to 20th	Night	33% 15% 20% 22% 10% 1	800
	21st to end	Night	32% 16% 20% 23% 7% 1	880
April	1st to 10th	Night	31% 14% 20% 24% 10% 2	800
	11th to 20th	Night	27% 13% 22% 25% 10% 2	791
	21st to end	Night	29% 14% 16% 27% 13% 1	554
May	1st to 10th	Night	23% 11% 17% 30% 17% 2	400
	11th to 20th	Night	25% 7% 14% 29% 23% 2	394
	21st to end	Night	26% 9% 13% 25% 24% 3	433
June	1st to 10th	Night	25% 8% 17% 26% 22% 3	400
	11th to 20th	Night	25% 12% 17% 29% 17% 1	400
	21st to end	Night	19% 7% 15% 27% 31% 2	400
July	1st to 10th	Night	13% 4 11% 34% 33% 4	380
	11th to 20th	Night	12% 3 8% 39% 34% 4	368
	21st to end	Night	8% 4 9% 30% 44% 5%	416
August	1st to 10th	Night	15% 2 6% 25% 42% 10%	420
	11th to 20th	Night	11% 2 8% 26% 41% 12%	564
	21st to end	Night	14% 6% 11% 31% 33% 5%	759
September	1st to 10th	Night	14% 4 11% 36% 30% 4	760
	11th to 20th	Night	18% 8% 13% 24% 31% 6%	760
	21st to end	Night	21% 7% 13% 31% 25% 3	760
October	1st to 10th	Night	24% 6% 16% 27% 24% 3	760
	11th to 20th	Night	28% 9% 17% 26% 17% 4	760
	21st to end	Night	32% 11% 18% 27% 9% 3	836
November	1st to 10th	Night	37% 11% 24% 22% 6%	780
	11th to 20th	Night	39% 13% 19% 23% 6% 1	800
	21st to end	Night	34% 13% 20% 23% 10%	800
December	1st to 10th	Night	30% 12% 22% 24% 11% 1	800
	11th to 20th	Night	40% 12% 22% 19% 6% 1	800
	21st to end	Night	45% 15% 19% 16% 4	880

Page generated at 2025-07-02 22:30:16. Version ac07

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