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 2024-01-16.

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	15% 11% 5% 8% 6% 4 5% 5% 5% 7% 31%	74594
	Night	14% 12% 5% 8% 7% 4 5% 4 5% 6% 30%	75178
Transparency	Day	52% 7% 12% 18% 10% 1	74300
	Night	54% 7% 12% 17% 9% 1	75007
Seeing	Day	20% 17% 31% 20% 9% 3	14409
	Night	19% 14% 32% 25% 9% 1	24157

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	14% 18% 8% 12% 9% 4 6% 4 4 5% 16%	1517
	11th to 20th	Day	15% 18% 8% 14% 10% 5% 6% 5% 4 5% 11%	1480
	21st to end	Day	12% 17% 9% 15% 11% 5% 6% 4 4 5% 12%	1584
February	1st to 10th	Day	11% 15% 9% 12% 14% 5% 6% 4 4 4 14%	1605
	11th to 20th	Day	12% 14% 8% 12% 11% 5% 5% 6% 4 4 21%	1697
	21st to end	Day	12% 19% 8% 12% 9% 3 4 4 4 6% 20%	1480
March	1st to 10th	Day	13% 11% 5% 10% 9% 4 4 5% 5% 4 28%	1798
	11th to 20th	Day	13% 12% 5% 9% 6% 3 5% 4 5% 6% 32%	1966
	21st to end	Day	17% 13% 4 7% 5% 4 4 4 5% 6% 31%	2196
April	1st to 10th	Day	19% 16% 5% 7% 5% 2 4 4 4 6% 27%	2160
	11th to 20th	Day	19% 14% 4 6% 4 2 4 3 4 6% 34%	2266
	21st to end	Day	16% 12% 4 8% 5% 3 5% 4 5% 6% 32%	2340
May	1st to 10th	Day	17% 9% 4 7% 5% 3 4 5% 6% 7% 34%	2340
	11th to 20th	Day	17% 8% 4 5% 5% 4 5% 5% 4 6% 38%	2305
	21st to end	Day	12% 5% 2 6% 6% 3 5% 5% 6% 7% 42%	2747
June	1st to 10th	Day	14% 6% 3 4 5% 3 5% 5% 6% 8% 41%	2700
	11th to 20th	Day	13% 7% 2 5% 5% 4 5% 5% 6% 8% 39%	2700
	21st to end	Day	14% 6% 3 6% 6% 4 4 5% 6% 9% 38%	2700
July	1st to 10th	Day	8% 4 2 5% 5% 3 5% 5% 6% 9% 47%	2534
	11th to 20th	Day	11% 5% 3 6% 5% 3 6% 6% 6% 9% 40%	2520
	21st to end	Day	10% 5% 3 5% 6% 4 5% 5% 6% 9% 41%	2743
August	1st to 10th	Day	9% 5% 3 6% 6% 4 6% 7% 7% 10% 37%	2347
	11th to 20th	Day	11% 6% 2 6% 6% 4 5% 5% 5% 8% 42%	2303
	21st to end	Day	14% 6% 3 6% 5% 3 5% 5% 5% 7% 41%	2531
September	1st to 10th	Day	14% 5% 3 5% 5% 3 5% 5% 5% 9% 40%	2095
	11th to 20th	Day	13% 5% 2 5% 5% 3 5% 5% 5% 7% 45%	1980
	21st to end	Day	17% 7% 3 7% 5% 4 5% 4 6% 8% 34%	1980
October	1st to 10th	Day	20% 9% 4 6% 6% 3 4 4 5% 6% 35%	1954
	11th to 20th	Day	24% 15% 4 8% 6% 2 4 4 5% 6% 21%	1751
	21st to end	Day	21% 17% 4 8% 7% 3 6% 5% 4 7% 17%	1782
November	1st to 10th	Day	14% 15% 5% 7% 6% 4 5% 5% 6% 7% 27%	1672
	11th to 20th	Day	14% 17% 8% 12% 7% 4 4 5% 5% 6% 19%	1710
	21st to end	Day	18% 19% 8% 12% 6% 3 4 3 4 5% 18%	1535
December	1st to 10th	Day	14% 19% 9% 15% 8% 4 5% 4 4 6% 14%	1364
	11th to 20th	Day	17% 18% 9% 12% 8% 4 4 4 5% 4 14%	1671
	21st to end	Day	23% 25% 10% 14% 7% 3 3 3 2 3 7%	2541
January	1st to 10th	Night	13% 15% 8% 13% 10% 5% 6% 5% 4 4 15%	2648
	11th to 20th	Night	16% 17% 8% 14% 11% 4 5% 4 4 5% 14%	2591
	21st to end	Night	12% 15% 8% 12% 10% 6% 7% 6% 5% 5% 14%	2772
February	1st to 10th	Night	11% 16% 7% 12% 12% 6% 6% 5% 5% 5% 16%	2354
	11th to 20th	Night	12% 15% 7% 12% 8% 5% 6% 5% 5% 5% 21%	2147
	21st to end	Night	15% 16% 6% 12% 8% 3 5% 4 4 4 24%	1776
March	1st to 10th	Night	12% 11% 5% 8% 6% 4 5% 5% 5% 5% 35%	2149
	11th to 20th	Night	14% 12% 5% 7% 5% 2 4 5% 5% 6% 35%	1993
	21st to end	Night	16% 10% 4 7% 5% 3 4 4 5% 5% 36%	2177
April	1st to 10th	Night	18% 13% 4 6% 6% 3 4 5% 6% 6% 29%	1800
	11th to 20th	Night	19% 11% 3 5% 5% 2 4 5% 5% 6% 35%	1643
	21st to end	Night	16% 9% 4 6% 5% 4 4 4 5% 6% 37%	1620
May	1st to 10th	Night	13% 8% 3 5% 7% 4 7% 6% 5% 7% 35%	1620
	11th to 20th	Night	14% 9% 4 6% 6% 3 4 6% 5% 7% 36%	1584
	21st to end	Night	12% 6% 2 4 4 3 5% 4 6% 10% 45%	1525
June	1st to 10th	Night	12% 5% 2 5% 5% 4 5% 6% 5% 7% 45%	1260
	11th to 20th	Night	8% 5% 2 5% 5% 3 6% 5% 7% 8% 46%	1260
	21st to end	Night	10% 6% 3 5% 5% 3 5% 4 6% 7% 46%	1260
July	1st to 10th	Night	6% 4 1 4 4 3 5% 4 7% 10% 54%	1421
	11th to 20th	Night	6% 5% 3 6% 5% 3 5% 5% 5% 8% 50%	1440
	21st to end	Night	8% 5% 2 5% 5% 2 5% 5% 6% 6% 51%	1575
August	1st to 10th	Night	8% 5% 2 5% 5% 3 4 4 5% 9% 49%	1588
	11th to 20th	Night	9% 4 2 4 5% 3 4 5% 5% 7% 53%	1598
	21st to end	Night	11% 6% 2 6% 5% 3 5% 4 5% 8% 46%	1822
September	1st to 10th	Night	12% 5% 3 5% 5% 2 4 4 4 7% 49%	1845
	11th to 20th	Night	13% 6% 2 5% 4 3 3 5% 4 6% 49%	1980
	21st to end	Night	18% 7% 3 6% 4 3 4 4 5% 8% 39%	1980
October	1st to 10th	Night	17% 8% 2 5% 5% 3 4 4 5% 7% 40%	2006
	11th to 20th	Night	20% 12% 4 7% 6% 3 4 4 4 6% 30%	2206
	21st to end	Night	23% 13% 4 6% 5% 3 4 4 5% 5% 26%	2574
November	1st to 10th	Night	13% 13% 5% 7% 6% 4 4 5% 5% 8% 31%	2406
	11th to 20th	Night	13% 16% 7% 9% 8% 3 5% 4 4 6% 24%	2470
	21st to end	Night	17% 17% 7% 10% 6% 3 4 4 5% 6% 21%	2641
December	1st to 10th	Night	14% 16% 8% 13% 9% 5% 6% 5% 5% 5% 15%	2813
	11th to 20th	Night	13% 18% 7% 15% 9% 4 5% 5% 5% 5% 14%	3526
	21st to end	Night	22% 26% 9% 12% 6% 3 4 3 3 3 9%	5108

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	70% 7% 10% 8% 4	1518
	11th to 20th	Day	75% 8% 6% 7% 3	1480
	21st to end	Day	76% 6% 7% 7% 4 1	1584
February	1st to 10th	Day	73% 6% 9% 10% 2	1605
	11th to 20th	Day	66% 6% 9% 11% 7% 1	1707
	21st to end	Day	65% 7% 9% 14% 5% 1	1480
March	1st to 10th	Day	58% 6% 12% 16% 8% 1	1800
	11th to 20th	Day	53% 6% 11% 20% 7% 3	1966
	21st to end	Day	54% 6% 10% 20% 10% 1	2196
April	1st to 10th	Day	58% 5% 11% 16% 8% 1	2160
	11th to 20th	Day	52% 5% 10% 17% 14% 1	2266
	21st to end	Day	52% 7% 12% 13% 13% 3	2340
May	1st to 10th	Day	48% 8% 10% 20% 12% 2	2340
	11th to 20th	Day	46% 6% 10% 21% 14% 2	2309
	21st to end	Day	39% 8% 14% 22% 14% 2	2747
June	1st to 10th	Day	39% 8% 13% 24% 14% 2	2700
	11th to 20th	Day	40% 9% 12% 21% 17% 2	2700
	21st to end	Day	42% 8% 13% 23% 13% 1	2700
July	1st to 10th	Day	32% 9% 12% 25% 19% 2	2465
	11th to 20th	Day	37% 9% 13% 24% 15% 2	2445
	21st to end	Day	37% 9% 14% 23% 16% 2	2591
August	1st to 10th	Day	40% 10% 15% 23% 11% 1	2332
	11th to 20th	Day	39% 10% 13% 24% 13% 2	2303
	21st to end	Day	41% 7% 14% 22% 13% 2	2531
September	1st to 10th	Day	41% 8% 13% 21% 15% 2	2095
	11th to 20th	Day	37% 7% 16% 27% 12% 1	1980
	21st to end	Day	47% 7% 14% 23% 8%	1980
October	1st to 10th	Day	50% 7% 10% 22% 10% 1	1954
	11th to 20th	Day	63% 7% 10% 15% 4	1751
	21st to end	Day	66% 7% 11% 11% 4	1782
November	1st to 10th	Day	55% 7% 12% 18% 8%	1672
	11th to 20th	Day	64% 7% 14% 10% 4	1710
	21st to end	Day	70% 5% 12% 9% 3	1535
December	1st to 10th	Day	74% 6% 9% 9% 2 1	1364
	11th to 20th	Day	73% 7% 9% 9% 2	1671
	21st to end	Day	85% 4 5% 4 2	2541
January	1st to 10th	Night	71% 6% 9% 9% 4	2648
	11th to 20th	Night	74% 7% 8% 7% 4	2591
	21st to end	Night	70% 8% 10% 9% 3	2772
February	1st to 10th	Night	69% 6% 9% 12% 4 1	2354
	11th to 20th	Night	63% 6% 10% 14% 5% 1	2148
	21st to end	Night	64% 6% 10% 14% 6%	1776
March	1st to 10th	Night	49% 6% 12% 22% 10% 1	2160
	11th to 20th	Night	50% 6% 11% 19% 12% 2	1994
	21st to end	Night	50% 6% 12% 18% 12% 2	2177
April	1st to 10th	Night	53% 7% 10% 17% 12% 1	1800
	11th to 20th	Night	48% 6% 11% 21% 14% 2	1643
	21st to end	Night	49% 6% 12% 18% 13% 3	1620
May	1st to 10th	Night	46% 7% 14% 18% 12% 4	1620
	11th to 20th	Night	47% 6% 8% 22% 14% 2	1585
	21st to end	Night	36% 6% 16% 24% 15% 3	1526
June	1st to 10th	Night	39% 6% 11% 26% 17% 1	1260
	11th to 20th	Night	33% 9% 14% 26% 16% 2	1260
	21st to end	Night	35% 9% 12% 26% 15% 3	1260
July	1st to 10th	Night	24% 7% 16% 32% 18% 2	1381
	11th to 20th	Night	30% 9% 14% 29% 17%	1392
	21st to end	Night	32% 9% 15% 27% 16% 1	1487
August	1st to 10th	Night	32% 8% 18% 28% 13% 1	1579
	11th to 20th	Night	29% 8% 18% 29% 15% 1	1598
	21st to end	Night	36% 7% 17% 23% 15% 2	1822
September	1st to 10th	Night	34% 8% 14% 26% 17% 2	1845
	11th to 20th	Night	35% 6% 16% 32% 11% 1	1980
	21st to end	Night	44% 8% 16% 25% 7%	1980
October	1st to 10th	Night	44% 7% 12% 24% 12% 1	2006
	11th to 20th	Night	54% 7% 13% 19% 6% 1	2206
	21st to end	Night	59% 7% 12% 16% 6%	2574
November	1st to 10th	Night	50% 8% 14% 20% 8% 1	2406
	11th to 20th	Night	61% 7% 14% 12% 6% 1	2470
	21st to end	Night	64% 8% 14% 11% 2 1	2641
December	1st to 10th	Night	70% 8% 9% 10% 2	2813
	11th to 20th	Night	70% 8% 11% 8% 2	3525
	21st to end	Night	81% 6% 7% 4 2	5108

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	26% 20% 38% 13% 3	270
	11th to 20th	Day	26% 22% 36% 13% 2	255
	21st to end	Day	27% 16% 40% 13% 5%	264
February	1st to 10th	Day	22% 34% 35% 6% 3	240
	11th to 20th	Day	23% 35% 33% 9%	240
	21st to end	Day	30% 31% 34% 5% 1	198
March	1st to 10th	Day	28% 30% 30% 10% 1	240
	11th to 20th	Day	23% 19% 36% 16% 5% 1	406
	21st to end	Day	29% 17% 27% 20% 6%	462
April	1st to 10th	Day	28% 18% 29% 19% 5% 1	420
	11th to 20th	Day	31% 19% 26% 14% 8% 2	412
	21st to end	Day	24% 19% 29% 19% 8% 2	420
May	1st to 10th	Day	23% 21% 31% 14% 7% 4	423
	11th to 20th	Day	18% 15% 32% 23% 9% 3	451
	21st to end	Day	15% 14% 33% 26% 10% 2	679
June	1st to 10th	Day	15% 17% 33% 23% 10% 1	630
	11th to 20th	Day	15% 14% 34% 25% 9% 3	630
	21st to end	Day	15% 12% 34% 27% 9% 3	630
July	1st to 10th	Day	9% 9% 33% 28% 15% 5%	621
	11th to 20th	Day	12% 11% 30% 28% 14% 5%	618
	21st to end	Day	10% 10% 35% 28% 11% 5%	684
August	1st to 10th	Day	10% 7% 30% 27% 17% 10%	466
	11th to 20th	Day	12% 7% 22% 32% 16% 10%	439
	21st to end	Day	17% 9% 29% 24% 17% 3	495
September	1st to 10th	Day	15% 11% 29% 23% 14% 7%	450
	11th to 20th	Day	12% 11% 24% 28% 16% 9%	450
	21st to end	Day	20% 12% 25% 26% 12% 6%	450
October	1st to 10th	Day	24% 17% 27% 18% 12% 2	450
	11th to 20th	Day	29% 22% 30% 15% 3 1	401
	21st to end	Day	32% 26% 29% 9% 3	297
November	1st to 10th	Day	27% 17% 35% 16% 4 1	270
	11th to 20th	Day	23% 28% 35% 11% 2 1	270
	21st to end	Day	22% 28% 35% 11% 2 1	187
December	1st to 10th	Day	29% 22% 33% 10% 4 2	180
	11th to 20th	Day	30% 24% 36% 8% 2	180
	21st to end	Day	30% 30% 29% 8% 3	231
January	1st to 10th	Night	20% 20% 36% 19% 5%	950
	11th to 20th	Night	24% 17% 34% 20% 5%	926
	21st to end	Night	18% 14% 40% 22% 5% 1	990
February	1st to 10th	Night	18% 21% 41% 18% 2	734
	11th to 20th	Night	20% 23% 33% 19% 5%	703
	21st to end	Night	28% 19% 32% 20% 2	592
March	1st to 10th	Night	17% 18% 37% 21% 7% 1	720
	11th to 20th	Night	21% 18% 34% 21% 5%	720
	21st to end	Night	20% 15% 33% 26% 6% 1	791
April	1st to 10th	Night	23% 16% 34% 21% 5% 1	540
	11th to 20th	Night	25% 12% 33% 24% 6% 1	533
	21st to end	Night	19% 13% 32% 29% 6% 1	540
May	1st to 10th	Night	15% 11% 39% 28% 7% 1	540
	11th to 20th	Night	18% 12% 30% 30% 10%	531
	21st to end	Night	13% 7% 31% 33% 15% 1	558
June	1st to 10th	Night	14% 7% 33% 37% 8% 1	360
	11th to 20th	Night	8% 8% 33% 39% 11%	360
	21st to end	Night	10% 7% 29% 40% 13% 1	360
July	1st to 10th	Night	7% 4 24% 45% 19% 1	506
	11th to 20th	Night	8% 4 27% 37% 21% 3	522
	21st to end	Night	10% 5% 25% 39% 19% 1	591
August	1st to 10th	Night	9% 2 24% 41% 22% 1	537
	11th to 20th	Night	10% 6% 19% 36% 27% 2	534
	21st to end	Night	14% 6% 22% 39% 18% 1	594
September	1st to 10th	Night	12% 5% 28% 31% 20% 4	585
	11th to 20th	Night	14% 8% 24% 33% 17% 4	720
	21st to end	Night	20% 10% 22% 31% 14% 4	720
October	1st to 10th	Night	22% 9% 28% 29% 12% 1	720
	11th to 20th	Night	28% 13% 32% 22% 6%	720
	21st to end	Night	30% 15% 31% 19% 5% 1	792
November	1st to 10th	Night	21% 17% 34% 21% 7% 1	740
	11th to 20th	Night	22% 20% 35% 19% 3	760
	21st to end	Night	25% 16% 39% 18% 2	760
December	1st to 10th	Night	24% 18% 35% 18% 4	913
	11th to 20th	Night	23% 21% 37% 15% 3 1	950
	21st to end	Night	27% 18% 37% 16% 2	1045

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