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 2026-10-29.

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	18% 9% 3 7% 5% 4 4 4 5% 6% 34%	154930
	Night	21% 10% 3 7% 5% 4 4 3 5% 6% 32%	145896
Transparency	Day	49% 8% 14% 18% 10% 2	154651
	Night	52% 8% 12% 17% 9% 2	145758
Seeing	Day	25% 14% 23% 25% 11% 3	17489
	Night	28% 11% 17% 26% 16% 2	25787

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	34% 16% 4 10% 5% 6% 4 3 4 5% 9%	4723
	11th to 20th	Day	18% 9% 3 7% 4 5% 5% 4 6% 8% 32%	4716
	21st to end	Day	28% 9% 3 7% 4 3 3 2 4 5% 32%	5348
February	1st to 10th	Day	29% 12% 4 8% 6% 4 5% 4 5% 6% 18%	1890
	11th to 20th	Day	29% 14% 4 7% 5% 4 4 3 4 4 19%	1845
	21st to end	Day	29% 17% 4 7% 5% 4 4 2 4 4 19%	1646
March	1st to 10th	Day	16% 13% 4 10% 7% 6% 7% 5% 7% 7% 20%	4703
	11th to 20th	Day	20% 16% 4 11% 6% 5% 4 3 3 3 25%	5110
	21st to end	Day	25% 14% 4 10% 6% 6% 5% 5% 6% 7% 12%	5820
April	1st to 10th	Day	25% 15% 3 8% 6% 6% 6% 5% 6% 5% 16%	2520
	11th to 20th	Day	22% 13% 3 8% 6% 5% 5% 4 5% 6% 23%	2492
	21st to end	Day	23% 13% 3 10% 6% 5% 4 4 4 5% 21%	2773
May	1st to 10th	Day	13% 8% 3 6% 4 5% 4 4 6% 7% 39%	8195
	11th to 20th	Day	18% 11% 4 9% 6% 5% 5% 5% 7% 7% 23%	8160
	21st to end	Day	20% 9% 3 7% 5% 4 5% 4 6% 8% 29%	8993
June	1st to 10th	Day	23% 9% 3 7% 5% 5% 4 4 5% 7% 27%	2940
	11th to 20th	Day	24% 11% 4 8% 6% 5% 6% 4 6% 6% 21%	3094
	21st to end	Day	15% 8% 3 6% 5% 5% 5% 4 6% 7% 36%	3150
July	1st to 10th	Day	8% 5% 2 5% 3 3 3 3 5% 6% 58%	8760
	11th to 20th	Day	5% 4 1 4 3 3 3 2 4 4 66%	8220
	21st to end	Day	8% 5% 2 5% 3 3 3 3 5% 7% 56%	8916
August	1st to 10th	Day	5% 3 1 3 3 3 3 3 5% 7% 64%	6331
	11th to 20th	Day	8% 6% 2 7% 5% 4 4 4 7% 8% 44%	5923
	21st to end	Day	14% 7% 3 7% 4 4 4 4 5% 8% 40%	6254
September	1st to 10th	Day	11% 6% 2 5% 4 3 5% 4 5% 7% 48%	2520
	11th to 20th	Day	15% 7% 2 8% 4 5% 4 4 6% 6% 39%	2520
	21st to end	Day	18% 6% 3 7% 5% 4 4 3 5% 6% 39%	2226
October	1st to 10th	Day	17% 6% 2 5% 4 3 3 4 6% 9% 40%	3380
	11th to 20th	Day	25% 8% 3 7% 5% 4 4 3 5% 6% 29%	3361
	21st to end	Day	26% 9% 4 9% 6% 5% 5% 4 4 6% 22%	3422
November	1st to 10th	Day	32% 10% 3 8% 5% 5% 4 4 5% 6% 18%	1722
	11th to 20th	Day	32% 13% 3 7% 4 4 5% 3 5% 4 20%	1680
	21st to end	Day	29% 13% 4 8% 4 4 4 3 5% 6% 21%	1680
December	1st to 10th	Day	24% 10% 2 6% 4 4 4 4 4 6% 33%	2700
	11th to 20th	Day	30% 11% 5% 9% 6% 5% 5% 4 5% 5% 16%	3105
	21st to end	Day	29% 13% 4 10% 6% 5% 5% 4 5% 4 14%	4092
January	1st to 10th	Night	31% 17% 5% 11% 6% 5% 4 3 4 4 10%	8172
	11th to 20th	Night	19% 10% 3 6% 4 3 4 4 7% 7% 33%	8182
	21st to end	Night	24% 9% 4 8% 4 4 4 4 4 5% 32%	8826
February	1st to 10th	Night	28% 14% 3 9% 6% 5% 4 3 4 5% 18%	2730
	11th to 20th	Night	27% 14% 3 7% 6% 4 4 3 4 5% 24%	2662
	21st to end	Night	26% 15% 3 7% 4 5% 5% 4 5% 5% 20%	2159
March	1st to 10th	Night	18% 13% 4 9% 6% 5% 5% 4 6% 7% 21%	5408
	11th to 20th	Night	22% 12% 4 8% 5% 5% 4 3 4 6% 27%	5109
	21st to end	Night	28% 15% 4 9% 6% 5% 5% 4 6% 5% 13%	5397
April	1st to 10th	Night	24% 13% 3 8% 6% 5% 5% 5% 5% 6% 19%	2100
	11th to 20th	Night	22% 11% 3 7% 6% 5% 4 4 5% 7% 27%	2079
	21st to end	Night	25% 11% 3 8% 5% 5% 5% 4 4 7% 24%	1842
May	1st to 10th	Night	16% 8% 3 5% 4 4 4 4 4 5% 43%	4724
	11th to 20th	Night	22% 12% 4 9% 6% 5% 5% 4 4 7% 22%	4700
	21st to end	Night	17% 11% 3 8% 5% 6% 5% 4 6% 8% 28%	5178
June	1st to 10th	Night	22% 10% 3 8% 5% 4 4 3 5% 7% 29%	1680
	11th to 20th	Night	18% 11% 3 8% 5% 4 4 4 5% 7% 29%	1519
	21st to end	Night	16% 7% 3 6% 3 4 3 3 5% 7% 42%	1470
July	1st to 10th	Night	8% 5% 2 5% 4 4 4 3 4 6% 56%	4195
	11th to 20th	Night	6% 3 1 3 2 2 3 3 3 5% 69%	4740
	21st to end	Night	10% 4 1 4 3 3 3 3 5% 6% 59%	5152
August	1st to 10th	Night	5% 2 1 3 2 2 2 2 3 5% 73%	3820
	11th to 20th	Night	11% 6% 3 6% 4 4 4 3 5% 8% 48%	4142
	21st to end	Night	17% 7% 2 5% 3 3 3 2 3 6% 48%	4907
September	1st to 10th	Night	12% 5% 2 5% 3 3 3 4 5% 7% 51%	2100
	11th to 20th	Night	16% 7% 3 8% 4 3 4 4 4 5% 42%	2100
	21st to end	Night	16% 6% 2 6% 5% 4 4 4 5% 7% 41%	2388
October	1st to 10th	Night	17% 5% 2 6% 4 4 4 3 5% 8% 42%	4040
	11th to 20th	Night	25% 8% 3 7% 3 4 4 4 5% 6% 32%	4017
	21st to end	Night	26% 10% 4 8% 5% 4 4 3 5% 7% 25%	4557
November	1st to 10th	Night	34% 9% 3 7% 5% 5% 4 4 5% 5% 20%	2795
	11th to 20th	Night	31% 12% 3 8% 6% 4 4 3 4 4 21%	2940
	21st to end	Night	28% 12% 4 8% 5% 3 4 4 5% 5% 22%	2940
December	1st to 10th	Night	22% 10% 2 7% 5% 4 4 3 5% 6% 32%	4700
	11th to 20th	Night	31% 15% 4 10% 6% 4 4 3 4 4 15%	5320
	21st to end	Night	27% 14% 5% 11% 6% 5% 5% 4 4 5% 14%	7106

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	76% 7% 6% 8% 3	4723
	11th to 20th	Day	47% 7% 10% 18% 17% 2	4740
	21st to end	Day	55% 6% 6% 17% 15% 2	5349
February	1st to 10th	Day	68% 7% 9% 9% 5% 1	1890
	11th to 20th	Day	68% 8% 7% 10% 6% 2	1854
	21st to end	Day	71% 7% 7% 11% 4	1646
March	1st to 10th	Day	58% 10% 16% 11% 6%	4703
	11th to 20th	Day	64% 7% 8% 20% 2	5110
	21st to end	Day	69% 11% 11% 7% 1	5820
April	1st to 10th	Day	69% 10% 12% 8% 1	2520
	11th to 20th	Day	62% 8% 11% 12% 6% 1	2492
	21st to end	Day	66% 8% 11% 11% 4 1	2773
May	1st to 10th	Day	43% 8% 18% 24% 7%	8195
	11th to 20th	Day	55% 15% 18% 11% 2	8163
	21st to end	Day	52% 11% 22% 13% 2	8994
June	1st to 10th	Day	58% 10% 14% 13% 5%	2940
	11th to 20th	Day	63% 10% 12% 12% 3	3094
	21st to end	Day	47% 10% 16% 17% 8% 1	3150
July	1st to 10th	Day	27% 7% 18% 21% 17% 10%	8687
	11th to 20th	Day	21% 6% 11% 25% 33% 5%	8145
	21st to end	Day	26% 7% 19% 33% 14% 1	8723
August	1st to 10th	Day	20% 5% 13% 29% 26% 6%	6314
	11th to 20th	Day	33% 11% 22% 26% 7% 1	5962
	21st to end	Day	41% 8% 15% 25% 11% 1	6253
September	1st to 10th	Day	34% 8% 17% 24% 13% 4	2520
	11th to 20th	Day	44% 9% 12% 18% 14% 3	2520
	21st to end	Day	44% 8% 17% 18% 11% 2	2226
October	1st to 10th	Day	40% 7% 13% 30% 10% 1	3380
	11th to 20th	Day	54% 7% 12% 16% 9% 1	3361
	21st to end	Day	61% 8% 11% 10% 8% 2	3422
November	1st to 10th	Day	66% 9% 11% 10% 3 1	1722
	11th to 20th	Day	70% 7% 8% 7% 6% 2	1680
	21st to end	Day	64% 8% 7% 10% 9% 2	1680
December	1st to 10th	Day	54% 6% 8% 17% 15% 2	2700
	11th to 20th	Day	69% 9% 10% 9% 3	3108
	21st to end	Day	71% 8% 9% 9% 2	4092
January	1st to 10th	Night	77% 6% 5% 8% 3 1	8172
	11th to 20th	Night	45% 6% 9% 18% 18% 2	8220
	21st to end	Night	54% 7% 7% 16% 14% 2	8826
February	1st to 10th	Night	67% 7% 9% 9% 6% 1	2730
	11th to 20th	Night	63% 8% 9% 10% 7% 3	2664
	21st to end	Night	67% 9% 9% 11% 4	2159
March	1st to 10th	Night	56% 10% 13% 13% 7%	5408
	11th to 20th	Night	57% 8% 13% 19% 2 1	5110
	21st to end	Night	67% 11% 12% 10% 1	5397
April	1st to 10th	Night	65% 11% 13% 9% 2	2100
	11th to 20th	Night	57% 10% 12% 13% 7% 1	2079
	21st to end	Night	62% 10% 11% 11% 5%	1842
May	1st to 10th	Night	43% 7% 15% 27% 9%	4721
	11th to 20th	Night	58% 12% 17% 12% 2	4700
	21st to end	Night	53% 11% 22% 13% 1	5182
June	1st to 10th	Night	56% 9% 14% 15% 6%	1680
	11th to 20th	Night	55% 9% 17% 16% 3	1519
	21st to end	Night	44% 9% 16% 21% 9% 2	1470
July	1st to 10th	Night	29% 8% 17% 20% 13% 13%	4160
	11th to 20th	Night	19% 4 11% 25% 36% 3	4692
	21st to end	Night	26% 6% 19% 33% 13% 3	5040
August	1st to 10th	Night	16% 4 10% 41% 25% 5%	3812
	11th to 20th	Night	34% 10% 22% 25% 8% 2	4169
	21st to end	Night	40% 7% 16% 25% 12% 1	4907
September	1st to 10th	Night	34% 8% 15% 23% 16% 4	2100
	11th to 20th	Night	45% 8% 9% 18% 15% 4	2100
	21st to end	Night	42% 10% 15% 18% 12% 4	2388
October	1st to 10th	Night	40% 7% 15% 28% 9% 1	4040
	11th to 20th	Night	53% 6% 11% 18% 10% 1	4017
	21st to end	Night	59% 7% 10% 14% 10%	4557
November	1st to 10th	Night	67% 8% 10% 11% 4 1	2795
	11th to 20th	Night	68% 7% 8% 9% 5% 2	2940
	21st to end	Night	65% 7% 7% 9% 10% 2	2940
December	1st to 10th	Night	52% 7% 9% 16% 15% 1	4700
	11th to 20th	Night	71% 8% 8% 9% 3	5316
	21st to end	Night	69% 11% 10% 7% 3	7106

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% 18% 14% 8% 3	220
	11th to 20th	Day	29% 17% 19% 21% 12% 2	220
	21st to end	Day	35% 16% 16% 19% 11% 2	300
February	1st to 10th	Day	39% 13% 23% 17% 7% 1	430
	11th to 20th	Day	39% 17% 22% 15% 5% 1	425
	21st to end	Day	38% 19% 22% 17% 4	402
March	1st to 10th	Day	31% 21% 25% 18% 5% 1	540
	11th to 20th	Day	33% 19% 22% 19% 6% 1	540
	21st to end	Day	34% 20% 24% 16% 6%	594
April	1st to 10th	Day	33% 17% 22% 19% 8% 1	540
	11th to 20th	Day	27% 22% 26% 15% 7% 2	532
	21st to end	Day	26% 19% 27% 19% 7% 2	540
May	1st to 10th	Day	19% 17% 27% 27% 8% 2	543
	11th to 20th	Day	31% 13% 25% 20% 9% 2	568
	21st to end	Day	27% 14% 23% 23% 10% 3	617
June	1st to 10th	Day	26% 12% 23% 24% 13% 3	570
	11th to 20th	Day	24% 16% 29% 21% 8% 2	724
	21st to end	Day	18% 11% 22% 33% 15% 2	780
July	1st to 10th	Day	13% 7% 24% 41% 13% 2	751
	11th to 20th	Day	10% 8% 27% 35% 16% 4	564
	21st to end	Day	10% 5% 23% 38% 20% 5%	619
August	1st to 10th	Day	11% 7% 18% 39% 18% 7%	567
	11th to 20th	Day	8% 5% 19% 41% 19% 6%	557
	21st to end	Day	12% 11% 25% 33% 13% 6%	627
September	1st to 10th	Day	14% 8% 23% 37% 13% 5%	570
	11th to 20th	Day	17% 12% 23% 30% 16% 3	570
	21st to end	Day	18% 14% 24% 28% 15% 2	570
October	1st to 10th	Day	23% 10% 23% 24% 17% 2	570
	11th to 20th	Day	28% 14% 21% 21% 12% 3	570
	21st to end	Day	30% 18% 22% 20% 7% 3	487
November	1st to 10th	Day	40% 15% 15% 19% 11%	260
	11th to 20th	Day	40% 17% 15% 13% 11% 4	220
	21st to end	Day	33% 13% 21% 18% 10% 5%	220
December	1st to 10th	Day	43% 13% 15% 11% 12% 6%	220
	11th to 20th	Day	41% 14% 23% 16% 6%	220
	21st to end	Day	40% 14% 19% 18% 10%	242
January	1st to 10th	Night	42% 14% 20% 17% 6%	840
	11th to 20th	Night	32% 13% 20% 23% 10% 1	840
	21st to end	Night	32% 11% 19% 28% 9% 1	924
February	1st to 10th	Night	36% 12% 22% 23% 7%	840
	11th to 20th	Night	33% 13% 17% 27% 9%	824
	21st to end	Night	35% 16% 21% 21% 6% 1	692
March	1st to 10th	Night	30% 16% 19% 24% 11% 1	840
	11th to 20th	Night	35% 14% 19% 21% 10% 1	840
	21st to end	Night	32% 16% 20% 23% 7% 1	924
April	1st to 10th	Night	30% 14% 20% 25% 10% 2	840
	11th to 20th	Night	27% 13% 22% 25% 10% 2	831
	21st to end	Night	29% 13% 17% 27% 12% 1	582
May	1st to 10th	Night	23% 11% 17% 30% 18% 1	420
	11th to 20th	Night	25% 7% 15% 29% 21% 1	414
	21st to end	Night	25% 10% 14% 26% 23% 2	455
June	1st to 10th	Night	26% 8% 16% 26% 20% 2	420
	11th to 20th	Night	24% 11% 17% 31% 17% 1	420
	21st to end	Night	19% 7% 14% 28% 30% 2	420
July	1st to 10th	Night	14% 4 10% 34% 35% 4	410
	11th to 20th	Night	12% 3 9% 41% 32% 3	408
	21st to end	Night	8% 4 9% 31% 44% 5%	460
August	1st to 10th	Night	15% 2 6% 26% 42% 9%	464
	11th to 20th	Night	12% 2 8% 26% 40% 11%	624
	21st to end	Night	14% 6% 11% 31% 34% 4	839
September	1st to 10th	Night	14% 4 12% 36% 31% 4	840
	11th to 20th	Night	17% 8% 13% 26% 31% 6%	840
	21st to end	Night	21% 7% 14% 31% 25% 3	840
October	1st to 10th	Night	22% 6% 17% 29% 24% 2	840
	11th to 20th	Night	27% 9% 18% 26% 16% 3	840
	21st to end	Night	31% 11% 19% 28% 9% 2	912
November	1st to 10th	Night	37% 12% 24% 21% 5%	820
	11th to 20th	Night	39% 13% 19% 22% 6% 1	840
	21st to end	Night	35% 13% 20% 23% 10%	840
December	1st to 10th	Night	32% 12% 21% 23% 10% 1	840
	11th to 20th	Night	42% 12% 22% 18% 6% 1	840
	21st to end	Night	44% 16% 19% 16% 5%	924

Page generated at 2026-10-26 01:37:52. Version ac07

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