Whiterock Resort
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiterock Resort clear sky chart from 2005-11-06 to 2024-04-25.

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	12% 8% 3 7% 6% 3 5% 5% 5% 7% 39%	83428
	Night	11% 8% 3 7% 5% 3 4 4 5% 7% 43%	85721
Transparency	Day	44% 6% 12% 23% 13% 2	83142
	Night	42% 5% 12% 24% 15% 2	85528
Seeing	Day	16% 11% 31% 27% 13% 3	15007
	Night	15% 10% 34% 30% 10% 1	25073

By Month

Percentage Cloud Cover SE (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	8% 12% 5% 15% 13% 5% 5% 4 4 6% 22%	2637
	11th to 20th	Day	8% 13% 5% 11% 9% 4 7% 5% 5% 6% 27%	2850
	21st to end	Day	13% 13% 7% 14% 8% 3 4 4 5% 5% 23%	3135
February	1st to 10th	Day	10% 13% 6% 8% 8% 4 5% 4 5% 7% 29%	1710
	11th to 20th	Day	10% 9% 5% 7% 7% 3 5% 4 4 7% 39%	1664
	21st to end	Day	13% 10% 5% 8% 5% 4 5% 4 5% 6% 35%	1529
March	1st to 10th	Day	14% 9% 4 7% 5% 3 3 3 3 5% 44%	3436
	11th to 20th	Day	11% 7% 3 6% 5% 3 4 4 5% 6% 44%	3480
	21st to end	Day	23% 13% 7% 8% 6% 3 4 5% 4 5% 21%	3814
April	1st to 10th	Day	17% 10% 3 5% 4 3 4 5% 5% 7% 37%	2222
	11th to 20th	Day	16% 10% 3 6% 6% 3 4 4 5% 7% 37%	2272
	21st to end	Day	21% 8% 3 5% 5% 3 4 4 5% 6% 36%	2394
May	1st to 10th	Day	18% 8% 3 6% 5% 3 5% 5% 6% 6% 34%	2340
	11th to 20th	Day	15% 8% 3 5% 7% 3 5% 5% 5% 7% 36%	2363
	21st to end	Day	16% 8% 3 6% 6% 4 5% 5% 5% 8% 35%	2725
June	1st to 10th	Day	10% 5% 3 5% 4 3 6% 5% 6% 9% 44%	2520
	11th to 20th	Day	9% 3 2 5% 5% 3 6% 6% 7% 9% 46%	2520
	21st to end	Day	7% 6% 2 5% 5% 4 6% 6% 7% 9% 44%	2520
July	1st to 10th	Day	8% 3 1 3 5% 3 4 4 7% 9% 51%	2520
	11th to 20th	Day	6% 4 1 3 5% 3 4 6% 6% 8% 53%	2409
	21st to end	Day	6% 4 2 5% 5% 4 5% 5% 7% 10% 47%	2546
August	1st to 10th	Day	8% 5% 3 6% 6% 3 6% 6% 7% 9% 40%	2328
	11th to 20th	Day	11% 5% 3 4 4 2 5% 4 6% 9% 47%	2301
	21st to end	Day	9% 4 2 5% 4 3 4 4 5% 7% 52%	2473
September	1st to 10th	Day	12% 5% 1 4 4 2 3 5% 5% 7% 52%	2160
	11th to 20th	Day	9% 6% 2 4 4 3 4 5% 5% 7% 53%	2027
	21st to end	Day	10% 5% 2 4 4 3 3 4 6% 8% 52%	1956
October	1st to 10th	Day	14% 6% 2 4 4 3 4 4 5% 6% 48%	1800
	11th to 20th	Day	14% 7% 3 4 5% 3 3 3 4 5% 49%	1800
	21st to end	Day	14% 9% 4 5% 4 3 4 4 4 6% 42%	1980
November	1st to 10th	Day	10% 5% 2 5% 4 3 3 5% 5% 8% 50%	1736
	11th to 20th	Day	12% 8% 3 7% 6% 3 4 5% 5% 7% 42%	1520
	21st to end	Day	13% 9% 4 4 5% 3 3 4 5% 8% 41%	1520
December	1st to 10th	Day	10% 8% 5% 7% 7% 3 5% 4 6% 7% 38%	1520
	11th to 20th	Day	10% 9% 4 8% 7% 4 5% 5% 6% 8% 33%	1918
	21st to end	Day	18% 12% 6% 15% 7% 3 4 4 5% 5% 21%	2783
January	1st to 10th	Night	8% 11% 5% 17% 11% 4 4 4 4 5% 26%	4300
	11th to 20th	Night	8% 13% 5% 9% 7% 4 7% 5% 9% 8% 26%	4120
	21st to end	Night	12% 14% 6% 12% 6% 3 3 3 4 6% 29%	4532
February	1st to 10th	Night	11% 12% 4 9% 8% 4 5% 4 4 5% 34%	2470
	11th to 20th	Night	10% 10% 4 6% 5% 4 5% 5% 5% 7% 40%	2403
	21st to end	Night	11% 8% 3 9% 5% 3 4 3 3 5% 44%	1940
March	1st to 10th	Night	13% 7% 3 5% 4 2 3 3 4 5% 49%	3419
	11th to 20th	Night	11% 7% 2 5% 4 2 3 3 5% 6% 52%	3480
	21st to end	Night	20% 11% 5% 10% 7% 3 5% 5% 5% 6% 23%	3817
April	1st to 10th	Night	13% 8% 2 6% 5% 2 4 5% 4 7% 45%	1957
	11th to 20th	Night	13% 8% 4 6% 5% 2 4 4 4 7% 42%	1853
	21st to end	Night	16% 8% 3 6% 5% 3 4 3 4 7% 40%	1665
May	1st to 10th	Night	16% 6% 2 4 6% 3 5% 5% 6% 7% 39%	1620
	11th to 20th	Night	15% 6% 2 4 5% 3 3 5% 6% 7% 44%	1532
	21st to end	Night	12% 7% 3 5% 5% 3 5% 5% 5% 9% 42%	1551
June	1st to 10th	Night	6% 4 3 3 5% 3 5% 5% 5% 10% 51%	1440
	11th to 20th	Night	7% 4 2 4 4 2 4 4 7% 9% 51%	1440
	21st to end	Night	4 3 2 5% 4 3 5% 6% 6% 8% 53%	1440
July	1st to 10th	Night	5% 3 1 4 3 2 4 6% 6% 9% 57%	1440
	11th to 20th	Night	4 2 1 3 3 2 3 4 5% 10% 63%	1547
	21st to end	Night	3 2 2 4 3 3 4 5% 6% 9% 58%	1772
August	1st to 10th	Night	7% 5% 2 5% 5% 3 5% 5% 5% 8% 50%	1611
	11th to 20th	Night	7% 4 2 4 4 2 3 4 5% 8% 57%	1600
	21st to end	Night	8% 4 2 4 3 2 4 4 5% 9% 56%	1881
September	1st to 10th	Night	9% 4 2 4 5% 3 3 3 4 7% 56%	1800
	11th to 20th	Night	9% 5% 2 3 3 2 4 4 5% 6% 56%	1930
	21st to end	Night	9% 4 2 4 4 1 3 4 4 6% 58%	1985
October	1st to 10th	Night	12% 6% 2 4 4 2 4 3 4 6% 51%	2160
	11th to 20th	Night	15% 6% 3 4 4 2 3 3 4 6% 50%	2160
	21st to end	Night	15% 7% 2 6% 3 2 4 3 3 6% 47%	2376
November	1st to 10th	Night	8% 5% 2 4 4 3 4 4 5% 6% 55%	2337
	11th to 20th	Night	12% 7% 3 6% 5% 3 4 4 5% 7% 46%	2660
	21st to end	Night	12% 8% 3 6% 5% 2 4 4 5% 6% 45%	2660
December	1st to 10th	Night	9% 9% 4 7% 7% 4 5% 4 6% 6% 39%	2660
	11th to 20th	Night	10% 9% 4 8% 5% 4 4 4 6% 6% 40%	3279
	21st to end	Night	18% 15% 6% 12% 7% 3 4 3 3 4 25%	4884

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	64% 5% 10% 14% 7%	2638
	11th to 20th	Day	59% 3 9% 22% 7%	2850
	21st to end	Day	63% 4 11% 14% 7%	3135
February	1st to 10th	Day	55% 4 10% 18% 10% 1	1710
	11th to 20th	Day	47% 4 12% 22% 14% 2	1673
	21st to end	Day	50% 5% 12% 19% 11% 3	1529
March	1st to 10th	Day	44% 4 9% 26% 15% 2	3436
	11th to 20th	Day	40% 6% 11% 25% 15% 3	3480
	21st to end	Day	65% 7% 10% 13% 4 1	3814
April	1st to 10th	Day	47% 6% 11% 26% 10% 1	2222
	11th to 20th	Day	48% 5% 12% 21% 13% 2	2272
	21st to end	Day	48% 5% 10% 23% 13%	2394
May	1st to 10th	Day	49% 6% 12% 20% 12% 1	2340
	11th to 20th	Day	47% 7% 11% 24% 10% 1	2367
	21st to end	Day	47% 7% 13% 19% 12% 2	2725
June	1st to 10th	Day	36% 7% 16% 25% 14% 2	2520
	11th to 20th	Day	33% 7% 14% 27% 18% 1	2520
	21st to end	Day	36% 7% 15% 25% 14% 3	2520
July	1st to 10th	Day	29% 7% 15% 32% 14% 3	2451
	11th to 20th	Day	28% 8% 13% 28% 19% 4	2336
	21st to end	Day	31% 7% 16% 28% 17% 2	2405
August	1st to 10th	Day	38% 9% 16% 23% 12% 2	2314
	11th to 20th	Day	34% 6% 12% 31% 15% 1	2301
	21st to end	Day	31% 6% 11% 28% 20% 4	2473
September	1st to 10th	Day	32% 5% 11% 28% 20% 4	2160
	11th to 20th	Day	31% 6% 12% 31% 19% 2	2027
	21st to end	Day	31% 5% 11% 31% 22% 1	1956
October	1st to 10th	Day	37% 4 10% 30% 17% 2	1800
	11th to 20th	Day	38% 3 8% 28% 19% 4	1800
	21st to end	Day	42% 6% 10% 21% 18% 3	1980
November	1st to 10th	Day	33% 5% 16% 24% 19% 3	1736
	11th to 20th	Day	43% 5% 12% 23% 17% 1	1520
	21st to end	Day	44% 4 14% 24% 14% 1	1520
December	1st to 10th	Day	45% 4 16% 22% 10% 2	1520
	11th to 20th	Day	49% 6% 16% 24% 6%	1915
	21st to end	Day	65% 5% 9% 15% 6% 1	2783
January	1st to 10th	Night	61% 4 10% 15% 10% 1	4300
	11th to 20th	Night	53% 5% 12% 18% 11% 2	4120
	21st to end	Night	58% 5% 11% 16% 10% 1	4532
February	1st to 10th	Night	53% 4 10% 20% 11% 2	2470
	11th to 20th	Night	44% 5% 11% 24% 14% 3	2404
	21st to end	Night	44% 3 11% 21% 18% 3	1940
March	1st to 10th	Night	38% 4 8% 28% 19% 3	3419
	11th to 20th	Night	34% 4 10% 32% 15% 5%	3480
	21st to end	Night	60% 9% 14% 12% 4 1	3817
April	1st to 10th	Night	40% 5% 11% 26% 16% 2	1957
	11th to 20th	Night	43% 5% 10% 24% 16% 3	1853
	21st to end	Night	44% 5% 11% 23% 16% 1	1665
May	1st to 10th	Night	42% 7% 13% 21% 14% 2	1620
	11th to 20th	Night	39% 7% 13% 25% 14% 2	1533
	21st to end	Night	40% 7% 16% 21% 12% 3	1552
June	1st to 10th	Night	29% 6% 15% 32% 15% 3	1440
	11th to 20th	Night	28% 7% 13% 24% 23% 4	1440
	21st to end	Night	26% 7% 15% 30% 19% 3	1440
July	1st to 10th	Night	23% 6% 16% 34% 18% 3	1400
	11th to 20th	Night	18% 5% 18% 34% 21% 4	1498
	21st to end	Night	21% 7% 16% 33% 20% 3	1673
August	1st to 10th	Night	32% 7% 16% 28% 15% 3	1601
	11th to 20th	Night	27% 6% 12% 32% 19% 3	1600
	21st to end	Night	26% 6% 12% 27% 22% 8%	1881
September	1st to 10th	Night	29% 5% 10% 27% 24% 4	1800
	11th to 20th	Night	28% 5% 10% 35% 21% 1	1930
	21st to end	Night	28% 4 10% 31% 24% 3	1985
October	1st to 10th	Night	34% 4 10% 28% 22% 2	2160
	11th to 20th	Night	37% 4 9% 24% 22% 5%	2160
	21st to end	Night	39% 3 13% 21% 21% 2	2376
November	1st to 10th	Night	30% 4 15% 26% 21% 4	2337
	11th to 20th	Night	38% 4 14% 26% 16% 2	2660
	21st to end	Night	41% 4 10% 28% 15% 2	2660
December	1st to 10th	Night	45% 3 14% 26% 11% 1	2660
	11th to 20th	Night	44% 5% 13% 30% 7% 1	3281
	21st to end	Night	64% 4 8% 17% 7% 1	4884

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	20% 16% 34% 22% 7% 1	270
	11th to 20th	Day	21% 14% 41% 21% 2 1	270
	21st to end	Day	22% 11% 38% 24% 4 1	297
February	1st to 10th	Day	18% 17% 44% 17% 3	270
	11th to 20th	Day	16% 21% 38% 20% 4 1	270
	21st to end	Day	24% 20% 38% 16% 3	225
March	1st to 10th	Day	16% 21% 42% 15% 6% 1	270
	11th to 20th	Day	26% 13% 38% 16% 6%	270
	21st to end	Day	32% 17% 34% 14% 3	297
April	1st to 10th	Day	27% 14% 34% 19% 5%	402
	11th to 20th	Day	22% 16% 34% 21% 7%	470
	21st to end	Day	23% 17% 33% 19% 6% 2	622
May	1st to 10th	Day	25% 13% 31% 23% 8% 1	603
	11th to 20th	Day	21% 13% 31% 23% 11% 2	625
	21st to end	Day	19% 10% 27% 25% 16% 3	679
June	1st to 10th	Day	9% 6% 27% 31% 23% 5%	630
	11th to 20th	Day	9% 5% 30% 36% 16% 3	630
	21st to end	Day	8% 8% 38% 29% 14% 3	630
July	1st to 10th	Day	7% 4 20% 34% 25% 11%	621
	11th to 20th	Day	6% 5% 28% 35% 20% 8%	618
	21st to end	Day	6% 2 23% 42% 23% 4	684
August	1st to 10th	Day	9% 4 21% 38% 22% 6%	626
	11th to 20th	Day	12% 5% 19% 34% 26% 5%	615
	21st to end	Day	10% 3 22% 38% 21% 6%	592
September	1st to 10th	Day	14% 6% 25% 34% 16% 6%	450
	11th to 20th	Day	10% 4 32% 31% 17% 6%	317
	21st to end	Day	13% 14% 29% 31% 13% 1	270
October	1st to 10th	Day	20% 10% 29% 26% 14% 2	270
	11th to 20th	Day	18% 19% 37% 20% 6% 1	270
	21st to end	Day	20% 16% 35% 19% 8% 1	297
November	1st to 10th	Day	14% 16% 40% 21% 7% 2	270
	11th to 20th	Day	20% 19% 36% 18% 7%	270
	21st to end	Day	21% 15% 39% 20% 6%	270
December	1st to 10th	Day	10% 13% 45% 23% 8%	270
	11th to 20th	Day	14% 16% 38% 22% 8% 1	270
	21st to end	Day	24% 18% 42% 13% 3	297
January	1st to 10th	Night	14% 16% 38% 26% 5%	950
	11th to 20th	Night	16% 15% 39% 23% 6% 1	950
	21st to end	Night	20% 11% 37% 26% 5%	1045
February	1st to 10th	Night	18% 12% 42% 24% 4	950
	11th to 20th	Night	17% 14% 40% 24% 4	929
	21st to end	Night	15% 17% 42% 20% 4 2	684
March	1st to 10th	Night	18% 11% 39% 24% 7% 1	570
	11th to 20th	Night	18% 9% 37% 28% 8%	570
	21st to end	Night	24% 13% 37% 20% 6% 1	627
April	1st to 10th	Night	19% 15% 38% 22% 5%	570
	11th to 20th	Night	18% 14% 34% 28% 5% 1	563
	21st to end	Night	19% 13% 35% 24% 8% 1	555
May	1st to 10th	Night	19% 9% 34% 29% 8%	540
	11th to 20th	Night	19% 9% 30% 31% 11%	531
	21st to end	Night	16% 7% 27% 35% 14%	584
June	1st to 10th	Night	8% 5% 25% 43% 19%	540
	11th to 20th	Night	10% 3 30% 43% 14%	540
	21st to end	Night	6% 5% 34% 40% 14% 1	540
July	1st to 10th	Night	5% 1 17% 45% 30% 2	525
	11th to 20th	Night	3 1 23% 50% 21% 2	522
	21st to end	Night	3 2 18% 51% 25% 1	591
August	1st to 10th	Night	9% 2 21% 41% 26% 1	537
	11th to 20th	Night	9% 2 19% 44% 24% 3	534
	21st to end	Night	9% 3 23% 40% 23% 3	594
September	1st to 10th	Night	10% 5% 21% 37% 23% 3	540
	11th to 20th	Night	12% 3 28% 37% 19% 1	540
	21st to end	Night	11% 6% 33% 34% 15% 2	545
October	1st to 10th	Night	16% 8% 33% 29% 13% 2	720
	11th to 20th	Night	18% 13% 36% 26% 8%	720
	21st to end	Night	20% 12% 32% 27% 8%	792
November	1st to 10th	Night	11% 14% 37% 30% 7%	830
	11th to 20th	Night	15% 16% 41% 22% 6%	950
	21st to end	Night	17% 12% 39% 25% 7% 1	950
December	1st to 10th	Night	15% 13% 42% 23% 7%	950
	11th to 20th	Night	16% 12% 38% 28% 5% 1	950
	21st to end	Night	20% 16% 37% 24% 4	1045

Page generated at 2024-04-22 08:25:43. Version ac07

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