Warbler's Hideaway Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Warbler's Hideaway Observatory clear sky chart from 2005-11-06 to 2025-10-04.

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	14% 11% 4 10% 5% 5% 4 4 5% 7% 31%	125776
	Night	13% 13% 5% 11% 6% 5% 4 3 5% 6% 30%	123745
Transparency	Day	51% 6% 11% 19% 11% 1	129282
	Night	54% 6% 12% 18% 10% 1	128326
Seeing	Day	20% 17% 31% 20% 9% 3	16828
	Night	19% 14% 32% 25% 9% 1	26356

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	10% 18% 8% 22% 8% 4 3 2 4 5% 16%	3617
	11th to 20th	Day	11% 17% 7% 22% 11% 10% 6% 3 3 4 7%	3589
	21st to end	Day	14% 18% 9% 16% 7% 4 4 3 4 6% 15%	3982
February	1st to 10th	Day	11% 17% 8% 14% 12% 6% 5% 4 4 4 15%	1784
	11th to 20th	Day	11% 15% 8% 15% 10% 6% 5% 4 3 4 20%	1892
	21st to end	Day	11% 20% 6% 13% 9% 4 4 3 4 6% 21%	1650
March	1st to 10th	Day	12% 11% 4 12% 5% 4 5% 4 4 6% 32%	4478
	11th to 20th	Day	12% 13% 5% 11% 5% 5% 5% 5% 6% 7% 26%	4952
	21st to end	Day	21% 12% 8% 12% 5% 4 4 3 4 4 24%	5510
April	1st to 10th	Day	17% 18% 4 8% 5% 4 5% 3 4 6% 27%	2400
	11th to 20th	Day	18% 14% 3 7% 3 4 3 3 4 5% 35%	2522
	21st to end	Day	15% 12% 4 9% 5% 4 4 4 5% 6% 32%	2600
May	1st to 10th	Day	17% 10% 3 7% 4 4 4 3 5% 7% 37%	5888
	11th to 20th	Day	13% 9% 3 6% 4 4 4 4 5% 6% 42%	5893
	21st to end	Day	15% 8% 2 7% 5% 4 4 3 5% 7% 40%	7013
June	1st to 10th	Day	13% 7% 2 5% 5% 5% 5% 4 6% 8% 40%	3000
	11th to 20th	Day	13% 7% 2 7% 5% 5% 5% 5% 7% 8% 38%	3000
	21st to end	Day	14% 7% 2 7% 5% 5% 4 4 6% 9% 37%	3000
July	1st to 10th	Day	13% 6% 2 7% 5% 4 4 4 5% 9% 40%	6373
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 6% 9% 44%	6360
	21st to end	Day	7% 5% 2 6% 4 5% 5% 4 7% 10% 45%	6926
August	1st to 10th	Day	9% 5% 2 7% 5% 6% 5% 5% 8% 10% 37%	4268
	11th to 20th	Day	13% 6% 2 6% 4 5% 4 4 5% 7% 42%	4174
	21st to end	Day	12% 6% 2 8% 5% 5% 5% 4 5% 7% 40%	4587
September	1st to 10th	Day	13% 6% 3 6% 5% 4 5% 4 6% 9% 40%	2327
	11th to 20th	Day	12% 5% 2 6% 4 3 5% 4 5% 7% 46%	2200
	21st to end	Day	16% 8% 3 7% 4 5% 5% 3 6% 8% 36%	2200
October	1st to 10th	Day	18% 9% 4 6% 5% 4 4 3 5% 6% 36%	2095
	11th to 20th	Day	22% 16% 4 9% 5% 4 4 3 5% 6% 23%	1848
	21st to end	Day	21% 17% 4 9% 6% 5% 6% 4 5% 7% 18%	1881
November	1st to 10th	Day	14% 17% 4 8% 5% 5% 4 3 6% 7% 27%	1762
	11th to 20th	Day	14% 19% 7% 13% 5% 4 4 4 5% 6% 19%	1800
	21st to end	Day	18% 20% 8% 13% 5% 4 3 3 4 5% 17%	1615
December	1st to 10th	Day	12% 25% 8% 19% 7% 5% 4 3 4 4 9%	2327
	11th to 20th	Day	15% 23% 9% 14% 7% 5% 4 3 4 4 12%	2621
	21st to end	Day	22% 26% 9% 16% 6% 3 3 2 3 3 8%	3642
January	1st to 10th	Night	10% 14% 9% 24% 9% 5% 4 3 3 4 15%	6348
	11th to 20th	Night	12% 15% 7% 19% 14% 8% 6% 3 3 4 8%	6316
	21st to end	Night	10% 19% 9% 17% 7% 6% 5% 4 5% 4 13%	6996
February	1st to 10th	Night	10% 17% 6% 14% 11% 7% 5% 4 5% 5% 17%	2615
	11th to 20th	Night	11% 16% 6% 14% 8% 6% 5% 4 5% 5% 20%	2392
	21st to end	Night	14% 16% 5% 14% 7% 4 4 4 4 5% 25%	1980
March	1st to 10th	Night	14% 10% 4 8% 6% 4 4 3 5% 6% 35%	5362
	11th to 20th	Night	10% 12% 5% 9% 4 4 5% 4 6% 7% 34%	5007
	21st to end	Night	19% 13% 5% 9% 5% 3 4 3 4 4 31%	5453
April	1st to 10th	Night	17% 14% 3 9% 4 4 4 4 5% 5% 31%	2000
	11th to 20th	Night	18% 12% 3 7% 4 3 3 4 5% 5% 35%	1827
	21st to end	Night	16% 10% 4 7% 5% 5% 4 3 5% 6% 36%	1800
May	1st to 10th	Night	14% 9% 3 7% 5% 4 5% 4 5% 7% 38%	4053
	11th to 20th	Night	15% 11% 3 6% 4 4 4 4 5% 6% 39%	3998
	21st to end	Night	18% 7% 2 5% 4 3 4 3 5% 7% 43%	3867
June	1st to 10th	Night	12% 6% 2 6% 4 4 4 5% 5% 7% 43%	1400
	11th to 20th	Night	8% 5% 2 6% 5% 5% 5% 4 7% 7% 45%	1400
	21st to end	Night	11% 7% 3 6% 4 4 5% 3 6% 7% 44%	1400
July	1st to 10th	Night	10% 7% 2 7% 4 5% 5% 4 7% 9% 41%	3573
	11th to 20th	Night	9% 6% 2 5% 3 4 4 3 5% 7% 52%	3620
	21st to end	Night	7% 5% 2 5% 4 3 4 4 5% 7% 52%	3948
August	1st to 10th	Night	9% 6% 2 7% 4 5% 4 4 6% 8% 45%	2879
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 5% 8% 49%	2875
	21st to end	Night	9% 6% 2 6% 4 4 4 3 6% 7% 48%	3307
September	1st to 10th	Night	11% 6% 2 6% 4 3 4 3 5% 7% 49%	2051
	11th to 20th	Night	12% 6% 2 5% 4 3 4 3 4 7% 51%	2200
	21st to end	Night	17% 7% 3 6% 4 4 4 3 5% 7% 40%	2200
October	1st to 10th	Night	16% 8% 2 6% 4 4 4 3 5% 7% 41%	2152
	11th to 20th	Night	19% 13% 3 8% 5% 4 4 3 4 6% 31%	2329
	21st to end	Night	22% 14% 4 7% 4 4 4 4 6% 5% 27%	2717
November	1st to 10th	Night	13% 14% 5% 8% 5% 4 4 4 6% 7% 31%	2536
	11th to 20th	Night	13% 18% 6% 10% 6% 5% 5% 4 4 5% 24%	2600
	21st to end	Night	17% 18% 7% 11% 6% 4 4 3 5% 6% 19%	2781
December	1st to 10th	Night	13% 17% 7% 16% 7% 6% 5% 4 5% 5% 14%	4859
	11th to 20th	Night	11% 24% 8% 15% 6% 4 4 3 5% 5% 14%	5586
	21st to end	Night	21% 26% 10% 12% 5% 4 3 2 3 3 10%	7318

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	71% 6% 10% 8% 4 1	3618
	11th to 20th	Day	81% 6% 5% 4 3	3620
	21st to end	Day	71% 5% 13% 6% 6%	3982
February	1st to 10th	Day	70% 6% 10% 10% 3	1784
	11th to 20th	Day	67% 6% 10% 10% 7% 1	1902
	21st to end	Day	63% 7% 9% 15% 5% 1	1650
March	1st to 10th	Day	51% 5% 15% 15% 10% 3	4480
	11th to 20th	Day	54% 7% 14% 17% 7% 1	4952
	21st to end	Day	63% 6% 8% 15% 8%	5510
April	1st to 10th	Day	58% 5% 11% 16% 9% 1	2400
	11th to 20th	Day	51% 6% 10% 18% 14% 1	2522
	21st to end	Day	51% 7% 11% 15% 14% 3	2600
May	1st to 10th	Day	45% 7% 10% 19% 17% 3	5897
	11th to 20th	Day	41% 7% 10% 23% 16% 2	5897
	21st to end	Day	43% 6% 10% 18% 19% 4	7013
June	1st to 10th	Day	40% 8% 13% 24% 14% 2	3000
	11th to 20th	Day	41% 8% 12% 21% 16% 2	3000
	21st to end	Day	42% 8% 13% 23% 13% 1	3000
July	1st to 10th	Day	40% 6% 12% 25% 16% 1	6305
	11th to 20th	Day	34% 7% 12% 32% 14% 1	6285
	21st to end	Day	33% 7% 14% 29% 16% 1	6728
August	1st to 10th	Day	38% 8% 13% 26% 14% 1	4253
	11th to 20th	Day	40% 8% 11% 27% 14% 1	4213
	21st to end	Day	42% 6% 14% 26% 11% 1	4586
September	1st to 10th	Day	40% 8% 14% 22% 14% 2	2327
	11th to 20th	Day	36% 7% 15% 27% 15% 1	2200
	21st to end	Day	46% 7% 13% 23% 11%	2200
October	1st to 10th	Day	35% 5% 9% 32% 18% 1	3459
	11th to 20th	Day	54% 5% 8% 20% 13%	3051
	21st to end	Day	62% 6% 11% 18% 4	3081
November	1st to 10th	Day	55% 7% 12% 18% 8%	1762
	11th to 20th	Day	64% 7% 14% 10% 5%	1800
	21st to end	Day	70% 5% 12% 9% 3	1615
December	1st to 10th	Day	79% 6% 7% 7% 1	2327
	11th to 20th	Day	76% 5% 8% 9% 2	2621
	21st to end	Day	83% 3 4 5% 5%	3642
January	1st to 10th	Night	73% 5% 7% 9% 4 1	6348
	11th to 20th	Night	78% 7% 7% 5% 2	6360
	21st to end	Night	72% 6% 9% 9% 4	6996
February	1st to 10th	Night	69% 6% 9% 11% 4 1	2615
	11th to 20th	Night	63% 7% 11% 14% 5% 1	2393
	21st to end	Night	61% 6% 11% 15% 6%	1980
March	1st to 10th	Night	49% 5% 17% 18% 10% 1	5373
	11th to 20th	Night	47% 7% 19% 19% 7% 1	5008
	21st to end	Night	56% 5% 11% 16% 11% 1	5453
April	1st to 10th	Night	53% 6% 10% 18% 11% 2	2000
	11th to 20th	Night	49% 5% 10% 20% 14% 2	1827
	21st to end	Night	50% 6% 11% 17% 14% 3	1800
May	1st to 10th	Night	43% 6% 12% 15% 19% 4	4060
	11th to 20th	Night	44% 6% 9% 24% 16% 1	3999
	21st to end	Night	41% 6% 12% 23% 14% 5%	3868
June	1st to 10th	Night	39% 6% 11% 27% 17% 1	1400
	11th to 20th	Night	34% 9% 14% 25% 16% 2	1400
	21st to end	Night	38% 8% 12% 25% 14% 2	1400
July	1st to 10th	Night	38% 6% 14% 26% 14% 3	3533
	11th to 20th	Night	31% 6% 11% 34% 17% 1	3572
	21st to end	Night	30% 8% 16% 30% 16%	3832
August	1st to 10th	Night	36% 7% 15% 28% 13% 1	2870
	11th to 20th	Night	34% 6% 17% 31% 12%	2902
	21st to end	Night	34% 7% 16% 27% 15% 1	3307
September	1st to 10th	Night	34% 7% 15% 27% 17% 1	2051
	11th to 20th	Night	34% 6% 15% 31% 13% 1	2200
	21st to end	Night	43% 8% 15% 25% 10% 1	2200
October	1st to 10th	Night	33% 6% 12% 33% 16% 1	3568
	11th to 20th	Night	46% 5% 10% 25% 14%	3865
	21st to end	Night	52% 6% 13% 24% 5%	4467
November	1st to 10th	Night	51% 8% 14% 20% 7% 1	2536
	11th to 20th	Night	61% 7% 13% 12% 6% 1	2600
	21st to end	Night	65% 8% 14% 11% 2 1	2781
December	1st to 10th	Night	69% 8% 11% 9% 2	4859
	11th to 20th	Night	71% 5% 9% 9% 4	5585
	21st to end	Night	79% 4 6% 5% 5%	7318

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	25% 20% 39% 12% 3	300
	11th to 20th	Day	25% 24% 36% 13% 2	300
	21st to end	Day	28% 15% 39% 12% 5%	330
February	1st to 10th	Day	22% 30% 36% 7% 4 1	300
	11th to 20th	Day	24% 33% 34% 9% 1	300
	21st to end	Day	29% 31% 34% 6% 1	249
March	1st to 10th	Day	27% 30% 32% 10% 1	300
	11th to 20th	Day	26% 20% 35% 15% 5% 1	485
	21st to end	Day	30% 19% 28% 19% 5%	550
April	1st to 10th	Day	30% 18% 29% 18% 4 1	500
	11th to 20th	Day	31% 21% 26% 13% 7% 2	492
	21st to end	Day	25% 20% 29% 18% 7% 2	500
May	1st to 10th	Day	23% 20% 32% 14% 7% 3	503
	11th to 20th	Day	18% 15% 32% 24% 9% 3	533
	21st to end	Day	18% 15% 31% 25% 9% 2	789
June	1st to 10th	Day	16% 17% 35% 22% 9% 1	730
	11th to 20th	Day	16% 15% 35% 23% 8% 3	730
	21st to end	Day	16% 14% 35% 25% 8% 2	730
July	1st to 10th	Day	11% 9% 35% 27% 13% 5%	721
	11th to 20th	Day	12% 11% 32% 27% 13% 5%	718
	21st to end	Day	10% 10% 35% 30% 11% 5%	794
August	1st to 10th	Day	9% 7% 29% 28% 17% 9%	548
	11th to 20th	Day	13% 7% 21% 33% 16% 10%	519
	21st to end	Day	16% 9% 30% 25% 17% 4	583
September	1st to 10th	Day	16% 12% 28% 23% 14% 7%	530
	11th to 20th	Day	11% 9% 23% 27% 18% 12%	530
	21st to end	Day	19% 11% 25% 27% 13% 5%	530
October	1st to 10th	Day	23% 17% 27% 19% 12% 2	502
	11th to 20th	Day	28% 21% 32% 15% 3 1	438
	21st to end	Day	32% 26% 30% 8% 3	330
November	1st to 10th	Day	29% 18% 33% 15% 4 1	300
	11th to 20th	Day	25% 27% 34% 11% 2 1	300
	21st to end	Day	23% 28% 35% 12% 2	207
December	1st to 10th	Day	32% 22% 32% 10% 4 2	200
	11th to 20th	Day	30% 24% 37% 9% 2	200
	21st to end	Day	32% 28% 27% 8% 4	257
January	1st to 10th	Night	20% 20% 37% 19% 4	1000
	11th to 20th	Night	23% 19% 34% 20% 4	1000
	21st to end	Night	18% 15% 40% 21% 5%	1100
February	1st to 10th	Night	18% 21% 40% 18% 3	815
	11th to 20th	Night	20% 24% 33% 19% 4	783
	21st to end	Night	26% 18% 34% 19% 2	660
March	1st to 10th	Night	18% 18% 37% 20% 6% 1	800
	11th to 20th	Night	21% 19% 34% 22% 5%	800
	21st to end	Night	21% 15% 33% 25% 5%	878
April	1st to 10th	Night	23% 16% 36% 20% 5% 1	600
	11th to 20th	Night	26% 12% 32% 22% 7% 1	593
	21st to end	Night	20% 13% 32% 28% 6% 1	600
May	1st to 10th	Night	14% 12% 37% 30% 7% 1	600
	11th to 20th	Night	18% 12% 29% 31% 10%	591
	21st to end	Night	15% 8% 30% 33% 14% 1	620
June	1st to 10th	Night	14% 8% 34% 37% 8% 1	400
	11th to 20th	Night	9% 9% 36% 38% 10%	400
	21st to end	Night	12% 8% 31% 36% 12% 1	400
July	1st to 10th	Night	7% 5% 24% 45% 18% 1	564
	11th to 20th	Night	8% 4 27% 37% 21% 3	582
	21st to end	Night	10% 5% 25% 40% 19% 1	657
August	1st to 10th	Night	10% 3 24% 41% 22% 1	597
	11th to 20th	Night	11% 6% 18% 36% 26% 2	594
	21st to end	Night	14% 5% 22% 39% 19% 1	660
September	1st to 10th	Night	12% 6% 28% 29% 21% 4	651
	11th to 20th	Night	14% 7% 22% 33% 20% 4	800
	21st to end	Night	20% 9% 21% 31% 15% 4	800
October	1st to 10th	Night	20% 10% 28% 30% 12% 1	773
	11th to 20th	Night	27% 13% 31% 23% 6%	760
	21st to end	Night	29% 15% 31% 20% 5% 1	836
November	1st to 10th	Night	22% 17% 33% 21% 7% 1	780
	11th to 20th	Night	23% 21% 34% 19% 3	800
	21st to end	Night	26% 16% 38% 17% 2	800
December	1st to 10th	Night	24% 18% 35% 18% 4	962
	11th to 20th	Night	23% 22% 36% 16% 3 1	1000
	21st to end	Night	27% 18% 36% 16% 3	1100

Page generated at 2025-10-01 01:39:01. Version ac07

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