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 2024-11-03.

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	20% 10% 3 7% 5% 4 4 3 5% 6% 32%	102177
	Night	23% 11% 3 7% 5% 4 4 3 4 5% 30%	96887
Transparency	Day	53% 9% 12% 16% 9% 2	101939
	Night	55% 9% 11% 15% 8% 2	96772
Seeing	Day	25% 14% 23% 25% 11% 2	14947
	Night	29% 11% 17% 25% 16% 2	23344

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	35% 17% 4 10% 5% 4 4 2 3 4 11%	2539
	11th to 20th	Day	24% 13% 3 8% 5% 4 4 4 4 6% 24%	2516
	21st to end	Day	38% 13% 3 9% 5% 3 4 2 4 5% 13%	2872
February	1st to 10th	Day	30% 12% 4 8% 6% 4 4 3 4 6% 18%	1710
	11th to 20th	Day	31% 14% 4 7% 5% 4 4 3 4 5% 19%	1665
	21st to end	Day	29% 17% 4 7% 5% 4 4 3 3 4 19%	1494
March	1st to 10th	Day	15% 13% 4 11% 8% 6% 6% 4 6% 6% 21%	3195
	11th to 20th	Day	19% 13% 3 8% 5% 4 4 2 3 4 36%	3490
	21st to end	Day	23% 16% 5% 11% 6% 6% 5% 4 5% 6% 14%	3969
April	1st to 10th	Day	27% 15% 3 8% 5% 6% 6% 5% 6% 5% 15%	2280
	11th to 20th	Day	23% 14% 3 8% 6% 4 5% 4 5% 6% 22%	2252
	21st to end	Day	25% 14% 3 11% 6% 5% 5% 3 4 5% 19%	2509
May	1st to 10th	Day	21% 10% 3 7% 5% 4 5% 4 5% 6% 32%	4420
	11th to 20th	Day	15% 10% 3 7% 5% 4 5% 4 6% 7% 32%	4377
	21st to end	Day	29% 12% 4 9% 6% 5% 5% 3 5% 5% 16%	4813
June	1st to 10th	Day	25% 10% 3 7% 6% 5% 4 3 5% 7% 25%	2660
	11th to 20th	Day	26% 11% 4 8% 6% 5% 6% 4 6% 6% 19%	2799
	21st to end	Day	14% 8% 3 6% 5% 5% 5% 4 6% 7% 37%	2850
July	1st to 10th	Day	8% 4 2 5% 2 2 3 3 4 5% 60%	4708
	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	21% 9% 3 7% 5% 4 4 4 5% 7% 33%	1900
	11th to 20th	Day	25% 8% 3 6% 5% 3 5% 4 5% 7% 30%	1900
	21st to end	Day	29% 9% 3 8% 5% 4 4 3 4 5% 26%	1971
November	1st to 10th	Day	32% 11% 3 7% 5% 5% 3 4 5% 6% 18%	1574
	11th to 20th	Day	32% 13% 3 7% 4 4 4 3 4 4 21%	1520
	21st to end	Day	30% 12% 3 8% 4 3 4 3 4 5% 22%	1520
December	1st to 10th	Day	28% 12% 3 6% 5% 5% 3 3 3 5% 26%	1520
	11th to 20th	Day	30% 11% 4 8% 4 4 5% 3 4 6% 19%	1925
	21st to end	Day	24% 13% 4 10% 6% 6% 6% 4 5% 5% 17%	2794
January	1st to 10th	Night	33% 18% 4 10% 5% 4 4 3 4 4 11%	4406
	11th to 20th	Night	27% 13% 4 7% 4 4 4 3 4 6% 23%	4382
	21st to end	Night	35% 12% 4 8% 5% 4 4 4 4 5% 15%	4772
February	1st to 10th	Night	30% 14% 3 9% 6% 4 4 3 4 5% 17%	2470
	11th to 20th	Night	28% 14% 3 7% 6% 4 4 3 4 4 24%	2402
	21st to end	Night	26% 15% 3 7% 4 5% 5% 4 5% 5% 20%	1960
March	1st to 10th	Night	17% 14% 5% 10% 6% 6% 6% 4 6% 8% 19%	3676
	11th to 20th	Night	19% 9% 3 7% 4 4 4 3 4 6% 37%	3489
	21st to end	Night	26% 17% 5% 10% 6% 5% 5% 3 5% 5% 14%	3684
April	1st to 10th	Night	25% 13% 3 8% 6% 5% 5% 5% 5% 6% 18%	1900
	11th to 20th	Night	22% 11% 3 7% 6% 5% 4 4 5% 6% 27%	1879
	21st to end	Night	26% 11% 3 8% 5% 5% 5% 4 5% 7% 21%	1667
May	1st to 10th	Night	22% 13% 3 6% 4 3 3 3 3 3 36%	2540
	11th to 20th	Night	18% 8% 3 7% 6% 5% 5% 4 5% 7% 32%	2516
	21st to end	Night	25% 14% 4 9% 5% 6% 5% 4 4 5% 20%	2762
June	1st to 10th	Night	22% 11% 3 8% 5% 4 4 3 5% 7% 28%	1520
	11th to 20th	Night	20% 12% 3 9% 5% 4 4 5% 4 7% 26%	1375
	21st to end	Night	15% 7% 3 6% 4 4 3 3 5% 7% 43%	1330
July	1st to 10th	Night	9% 5% 2 5% 3 3 3 2 4 5% 60%	2247
	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	21% 6% 3 6% 4 4 4 3 4 6% 38%	2280
	11th to 20th	Night	25% 8% 4 7% 4 4 4 3 4 4 33%	2280
	21st to end	Night	28% 8% 3 6% 4 4 3 3 5% 7% 29%	2626
November	1st to 10th	Night	35% 8% 3 7% 5% 5% 4 4 5% 5% 20%	2548
	11th to 20th	Night	30% 12% 3 8% 5% 4 4 3 4 4 22%	2660
	21st to end	Night	28% 12% 4 8% 5% 3 4 4 5% 5% 22%	2660
December	1st to 10th	Night	27% 12% 3 8% 6% 4 4 4 4 4 24%	2660
	11th to 20th	Night	28% 13% 4 9% 5% 4 4 3 5% 4 20%	3280
	21st to end	Night	25% 14% 5% 11% 7% 5% 5% 4 4 4 15%	4862

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% 7% 3 1	2539
	11th to 20th	Day	61% 9% 11% 12% 6% 2	2540
	21st to end	Day	71% 9% 7% 8% 4 1	2872
February	1st to 10th	Day	68% 8% 10% 9% 5% 1	1710
	11th to 20th	Day	68% 8% 7% 10% 5% 2	1674
	21st to end	Day	71% 7% 7% 11% 4	1494
March	1st to 10th	Day	58% 11% 14% 12% 4	3195
	11th to 20th	Day	54% 6% 9% 28% 2 1	3490
	21st to end	Day	70% 12% 10% 7% 1	3969
April	1st to 10th	Day	71% 10% 11% 7% 1	2280
	11th to 20th	Day	64% 8% 10% 10% 6% 1	2252
	21st to end	Day	70% 8% 9% 9% 3 1	2509
May	1st to 10th	Day	53% 9% 12% 17% 8%	4420
	11th to 20th	Day	46% 16% 19% 16% 3	4380
	21st to end	Day	69% 12% 12% 7%	4814
June	1st to 10th	Day	61% 10% 14% 11% 4	2660
	11th to 20th	Day	66% 10% 11% 10% 2	2799
	21st to end	Day	46% 10% 17% 17% 9% 1	2850
July	1st to 10th	Day	26% 6% 10% 19% 20% 19%	4635
	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	50% 8% 11% 20% 10% 1	1900
	11th to 20th	Day	53% 8% 14% 17% 7% 1	1900
	21st to end	Day	60% 7% 9% 13% 10% 1	1971
November	1st to 10th	Day	67% 8% 11% 9% 4 1	1574
	11th to 20th	Day	69% 7% 8% 7% 7% 2	1520
	21st to end	Day	64% 8% 6% 10% 10% 2	1520
December	1st to 10th	Day	62% 8% 10% 10% 8% 2	1520
	11th to 20th	Day	65% 9% 11% 10% 5% 1	1928
	21st to end	Day	66% 10% 11% 10% 3	2794
January	1st to 10th	Night	77% 7% 6% 6% 2 1	4406
	11th to 20th	Night	61% 8% 9% 15% 6% 2	4420
	21st to end	Night	69% 10% 8% 7% 6% 1	4772
February	1st to 10th	Night	69% 8% 9% 9% 5% 1	2470
	11th to 20th	Night	63% 8% 9% 10% 6% 3	2404
	21st to end	Night	67% 9% 9% 10% 4	1960
March	1st to 10th	Night	57% 11% 14% 13% 5%	3676
	11th to 20th	Night	47% 8% 16% 26% 3 1	3490
	21st to end	Night	68% 13% 11% 8%	3684
April	1st to 10th	Night	67% 11% 12% 9% 1	1900
	11th to 20th	Night	58% 10% 11% 13% 7% 1	1879
	21st to end	Night	66% 10% 9% 10% 5% 1	1667
May	1st to 10th	Night	51% 7% 11% 20% 9%	2540
	11th to 20th	Night	45% 14% 20% 17% 3 1	2516
	21st to end	Night	66% 12% 12% 9% 1	2762
June	1st to 10th	Night	57% 10% 14% 14% 5%	1520
	11th to 20th	Night	59% 9% 17% 12% 3	1375
	21st to end	Night	43% 9% 17% 20% 9% 2	1330
July	1st to 10th	Night	27% 7% 10% 17% 15% 24%	2212
	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	46% 8% 13% 22% 10% 1	2280
	11th to 20th	Night	54% 7% 10% 19% 9% 1	2280
	21st to end	Night	56% 8% 9% 15% 11% 1	2626
November	1st to 10th	Night	66% 8% 10% 11% 4 1	2548
	11th to 20th	Night	66% 7% 8% 10% 6% 3	2660
	21st to end	Night	65% 7% 7% 9% 11% 2	2660
December	1st to 10th	Night	63% 8% 8% 10% 8% 2	2660
	11th to 20th	Night	65% 9% 11% 10% 5% 1	3276
	21st to end	Night	67% 12% 10% 8% 4	4862

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	37% 19% 19% 11% 10% 3	180
	11th to 20th	Day	32% 19% 20% 18% 9% 1	180
	21st to end	Day	38% 19% 17% 16% 10% 1	250
February	1st to 10th	Day	40% 14% 22% 16% 6% 1	370
	11th to 20th	Day	42% 16% 22% 15% 5% 1	365
	21st to end	Day	37% 19% 22% 17% 4 1	346
March	1st to 10th	Day	29% 22% 26% 18% 5%	460
	11th to 20th	Day	29% 19% 23% 20% 8% 1	460
	21st to end	Day	34% 21% 24% 16% 6%	506
April	1st to 10th	Day	35% 19% 20% 17% 7% 1	460
	11th to 20th	Day	29% 23% 27% 12% 6% 2	452
	21st to end	Day	28% 20% 28% 18% 6% 1	460
May	1st to 10th	Day	21% 17% 27% 26% 7% 2	463
	11th to 20th	Day	30% 11% 25% 20% 10% 3	488
	21st to end	Day	29% 15% 22% 23% 9% 2	529
June	1st to 10th	Day	28% 11% 23% 23% 13% 2	490
	11th to 20th	Day	27% 17% 28% 19% 8% 2	629
	21st to end	Day	17% 10% 22% 33% 15% 3	680
July	1st to 10th	Day	14% 8% 23% 40% 13% 2	653
	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% 21% 6% 4	420
November	1st to 10th	Day	42% 14% 15% 19% 10%	220
	11th to 20th	Day	39% 18% 13% 12% 13% 4	180
	21st to end	Day	33% 14% 22% 14% 12% 5%	180
December	1st to 10th	Day	42% 15% 17% 9% 11% 6%	180
	11th to 20th	Day	39% 14% 23% 17% 7% 1	180
	21st to end	Day	39% 15% 19% 18% 9% 1	198
January	1st to 10th	Night	43% 15% 19% 17% 6% 1	760
	11th to 20th	Night	34% 14% 19% 22% 9% 1	760
	21st to end	Night	34% 12% 18% 27% 8% 1	836
February	1st to 10th	Night	38% 11% 20% 23% 7% 1	760
	11th to 20th	Night	34% 13% 17% 26% 9%	744
	21st to end	Night	35% 16% 20% 21% 6% 1	628
March	1st to 10th	Night	29% 17% 19% 24% 11% 1	760
	11th to 20th	Night	31% 15% 20% 22% 11% 1	760
	21st to end	Night	32% 17% 20% 23% 8% 1	836
April	1st to 10th	Night	31% 14% 19% 24% 10% 2	760
	11th to 20th	Night	27% 13% 22% 25% 10% 2	751
	21st to end	Night	30% 14% 17% 26% 12% 1	527
May	1st to 10th	Night	24% 12% 18% 28% 17% 2	380
	11th to 20th	Night	24% 7% 14% 30% 24% 2	374
	21st to end	Night	27% 9% 14% 25% 23% 3	411
June	1st to 10th	Night	26% 9% 16% 26% 20% 3	380
	11th to 20th	Night	26% 11% 17% 28% 18% 1	380
	21st to end	Night	18% 6% 15% 28% 31% 2	380
July	1st to 10th	Night	14% 4 11% 34% 34% 4	370
	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% 21% 6%	748
	11th to 20th	Night	38% 13% 19% 23% 6% 1	760
	21st to end	Night	35% 13% 19% 23% 10%	760
December	1st to 10th	Night	31% 13% 22% 24% 9% 1	760
	11th to 20th	Night	40% 11% 22% 19% 7% 1	760
	21st to end	Night	45% 15% 19% 17% 5%	836

Page generated at 2024-10-31 00:39:26. Version ac07

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