Davis Creek Reservoir
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Davis Creek Reservoir clear sky chart from 2005-11-06 to 2024-01-13.

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	10% 6% 3 5% 4 3 4 4 5% 7% 49%	74966
	Night	9% 6% 2 5% 4 2 4 4 5% 7% 51%	74781
Transparency	Day	34% 6% 14% 26% 16% 3	74682
	Night	32% 6% 14% 27% 18% 3	74588
Seeing	Day	12% 9% 31% 31% 14% 2	14625
	Night	11% 9% 35% 35% 9%	24667

By Month

Percentage Cloud Cover SW (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% 11% 3 6% 5% 3 4 3 4 8% 47%	1518
	11th to 20th	Day	7% 10% 2 5% 5% 3 5% 5% 5% 7% 47%	1469
	21st to end	Day	8% 9% 4 9% 7% 3 5% 4 5% 6% 41%	1782
February	1st to 10th	Day	9% 8% 5% 9% 6% 3 4 4 5% 8% 40%	1620
	11th to 20th	Day	7% 8% 3 7% 4 4 4 4 6% 6% 46%	1745
	21st to end	Day	10% 8% 3 5% 4 3 4 3 4 7% 48%	1480
March	1st to 10th	Day	9% 6% 2 4 3 3 4 4 4 6% 53%	1831
	11th to 20th	Day	12% 8% 3 4 4 2 3 5% 5% 7% 47%	1980
	21st to end	Day	14% 10% 5% 7% 5% 3 4 5% 5% 6% 36%	2178
April	1st to 10th	Day	12% 7% 3 5% 5% 3 4 4 5% 7% 46%	2086
	11th to 20th	Day	15% 7% 3 5% 5% 3 3 4 5% 8% 43%	2245
	21st to end	Day	17% 6% 3 4 5% 3 4 4 5% 8% 42%	2340
May	1st to 10th	Day	14% 6% 3 5% 6% 3 5% 4 6% 7% 41%	2340
	11th to 20th	Day	17% 7% 3 5% 5% 3 4 4 4 7% 42%	2302
	21st to end	Day	14% 6% 3 5% 6% 4 4 5% 6% 8% 39%	2531
June	1st to 10th	Day	6% 4 2 4 4 2 5% 5% 7% 9% 52%	2459
	11th to 20th	Day	11% 4 2 4 4 3 4 5% 6% 8% 51%	2520
	21st to end	Day	5% 4 2 3 4 2 4 5% 7% 10% 56%	2520
July	1st to 10th	Day	7% 4 2 4 4 3 4 5% 7% 9% 51%	2520
	11th to 20th	Day	5% 3 1 4 4 3 4 4 5% 9% 58%	2520
	21st to end	Day	6% 4 2 4 4 3 5% 5% 7% 10% 50%	2555
August	1st to 10th	Day	7% 6% 2 5% 5% 3 5% 6% 8% 9% 44%	2328
	11th to 20th	Day	7% 4 2 4 4 3 4 4 6% 9% 53%	2301
	21st to end	Day	8% 5% 2 4 3 2 4 4 6% 7% 56%	2500
September	1st to 10th	Day	12% 5% 2 4 3 2 3 4 4 6% 54%	2057
	11th to 20th	Day	8% 4 2 4 4 3 4 4 4 7% 57%	1980
	21st to end	Day	11% 4 2 3 3 2 3 3 3 6% 61%	1980
October	1st to 10th	Day	15% 5% 2 4 3 2 3 3 4 5% 54%	1956
	11th to 20th	Day	10% 5% 2 5% 3 2 3 3 4 6% 59%	1800
	21st to end	Day	14% 6% 2 5% 3 2 3 3 3 5% 54%	1836
November	1st to 10th	Day	8% 4 1 4 4 3 4 5% 6% 7% 53%	1673
	11th to 20th	Day	6% 5% 2 5% 5% 3 3 4 4 5% 57%	1710
	21st to end	Day	9% 7% 3 5% 3 3 3 4 4 6% 52%	1710
December	1st to 10th	Day	7% 7% 4 6% 4 2 3 4 6% 8% 50%	1710
	11th to 20th	Day	6% 7% 4 6% 5% 3 5% 4 6% 7% 47%	2090
	21st to end	Day	11% 13% 5% 11% 5% 3 4 4 4 5% 37%	2794
January	1st to 10th	Night	7% 7% 3 6% 6% 3 5% 4 5% 7% 47%	2647
	11th to 20th	Night	6% 9% 3 6% 5% 3 4 4 6% 7% 46%	2533
	21st to end	Night	6% 8% 4 7% 5% 3 4 5% 5% 9% 43%	2574
February	1st to 10th	Night	9% 9% 4 7% 5% 2 4 5% 5% 6% 43%	2340
	11th to 20th	Night	5% 8% 3 5% 6% 3 6% 5% 6% 7% 45%	2116
	21st to end	Night	7% 8% 3 5% 5% 3 4 4 4 7% 52%	1776
March	1st to 10th	Night	9% 6% 3 5% 5% 2 4 4 5% 6% 51%	2129
	11th to 20th	Night	12% 8% 2 5% 4 2 4 4 5% 7% 49%	1980
	21st to end	Night	14% 9% 4 6% 5% 3 4 5% 5% 7% 39%	2178
April	1st to 10th	Night	13% 6% 3 4 4 2 4 5% 5% 7% 46%	1872
	11th to 20th	Night	13% 6% 3 4 4 3 5% 4 6% 8% 44%	1663
	21st to end	Night	14% 6% 2 4 4 2 4 4 6% 7% 48%	1620
May	1st to 10th	Night	13% 5% 2 5% 6% 3 4 5% 6% 7% 45%	1620
	11th to 20th	Night	14% 6% 2 3 5% 3 4 5% 6% 9% 44%	1593
	21st to end	Night	15% 5% 2 5% 4 2 4 6% 7% 10% 40%	1745
June	1st to 10th	Night	8% 3 1 4 3 2 4 5% 7% 10% 53%	1495
	11th to 20th	Night	10% 4 2 4 3 2 4 3 5% 8% 55%	1440
	21st to end	Night	4 4 2 4 4 3 5% 5% 6% 9% 55%	1440
July	1st to 10th	Night	7% 3 2 4 4 2 4 4 6% 9% 54%	1440
	11th to 20th	Night	3 2 1 2 4 2 5% 5% 6% 9% 59%	1440
	21st to end	Night	4 3 2 4 5% 3 4 5% 7% 11% 52%	1762
August	1st to 10th	Night	6% 3 3 3 5% 3 5% 6% 7% 10% 49%	1611
	11th to 20th	Night	6% 3 1 4 4 2 5% 4 5% 9% 57%	1600
	21st to end	Night	7% 4 1 3 3 3 3 4 5% 7% 60%	1853
September	1st to 10th	Night	9% 3 1 4 3 2 3 3 4 5% 63%	1902
	11th to 20th	Night	7% 4 2 3 4 3 3 4 5% 6% 61%	1980
	21st to end	Night	8% 4 2 3 4 2 3 4 4 6% 62%	1980
October	1st to 10th	Night	16% 5% 1 4 4 2 3 3 6% 7% 51%	1984
	11th to 20th	Night	10% 5% 2 3 3 2 2 3 4 6% 60%	2160
	21st to end	Night	12% 5% 2 4 3 2 3 3 4 6% 56%	2518
November	1st to 10th	Night	5% 4 1 3 3 2 4 5% 5% 8% 60%	2405
	11th to 20th	Night	8% 6% 2 3 5% 2 4 3 5% 6% 57%	2470
	21st to end	Night	7% 6% 3 4 4 2 3 4 4 7% 55%	2470
December	1st to 10th	Night	6% 7% 2 5% 6% 3 4 4 4 7% 53%	2470
	11th to 20th	Night	7% 5% 3 5% 4 2 3 4 6% 8% 52%	3102
	21st to end	Night	14% 11% 3 8% 4 2 3 4 4 6% 39%	4873

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	39% 6% 15% 26% 14% 2	1519
	11th to 20th	Day	38% 5% 18% 21% 16% 2	1469
	21st to end	Day	44% 6% 15% 21% 12% 2	1782
February	1st to 10th	Day	43% 7% 14% 21% 12% 2	1620
	11th to 20th	Day	37% 6% 15% 23% 15% 4	1755
	21st to end	Day	36% 5% 15% 24% 14% 5%	1480
March	1st to 10th	Day	32% 5% 13% 26% 20% 3	1831
	11th to 20th	Day	37% 6% 12% 27% 15% 2	1980
	21st to end	Day	47% 7% 16% 21% 8% 1	2178
April	1st to 10th	Day	37% 6% 15% 26% 13% 2	2086
	11th to 20th	Day	40% 5% 16% 22% 14% 3	2248
	21st to end	Day	41% 6% 12% 28% 13% 1	2340
May	1st to 10th	Day	41% 8% 15% 22% 13% 2	2340
	11th to 20th	Day	42% 7% 17% 24% 11%	2306
	21st to end	Day	41% 9% 16% 22% 10% 2	2531
June	1st to 10th	Day	27% 8% 20% 31% 13% 2	2459
	11th to 20th	Day	30% 7% 15% 25% 18% 4	2520
	21st to end	Day	22% 9% 18% 31% 17% 4	2520
July	1st to 10th	Day	27% 8% 16% 30% 16% 2	2451
	11th to 20th	Day	24% 6% 14% 29% 22% 5%	2445
	21st to end	Day	26% 9% 17% 31% 15% 1	2413
August	1st to 10th	Day	32% 11% 18% 24% 13% 2	2314
	11th to 20th	Day	27% 7% 16% 33% 16% 1	2301
	21st to end	Day	28% 7% 13% 24% 23% 6%	2500
September	1st to 10th	Day	31% 5% 13% 22% 22% 7%	2057
	11th to 20th	Day	26% 7% 13% 30% 21% 3	1980
	21st to end	Day	26% 4 10% 33% 26% 1	1980
October	1st to 10th	Day	33% 4 10% 28% 23% 2	1956
	11th to 20th	Day	29% 3 10% 29% 22% 7%	1800
	21st to end	Day	35% 4 12% 23% 21% 5%	1836
November	1st to 10th	Day	28% 7% 15% 27% 21% 3	1673
	11th to 20th	Day	28% 6% 12% 27% 23% 5%	1710
	21st to end	Day	34% 4 13% 28% 18% 4	1710
December	1st to 10th	Day	33% 6% 14% 30% 14% 3	1710
	11th to 20th	Day	35% 6% 15% 32% 12%	2088
	21st to end	Day	51% 5% 8% 24% 11% 1	2794
January	1st to 10th	Night	37% 6% 11% 28% 16% 2	2647
	11th to 20th	Night	36% 6% 15% 27% 14% 1	2533
	21st to end	Night	38% 6% 16% 26% 12% 2	2574
February	1st to 10th	Night	41% 6% 13% 23% 14% 3	2340
	11th to 20th	Night	35% 8% 14% 26% 14% 3	2116
	21st to end	Night	33% 5% 13% 25% 19% 5%	1776
March	1st to 10th	Night	34% 5% 12% 28% 18% 3	2129
	11th to 20th	Night	35% 5% 10% 24% 23% 3	1980
	21st to end	Night	44% 7% 15% 22% 12% 2	2178
April	1st to 10th	Night	36% 7% 15% 23% 17% 2	1872
	11th to 20th	Night	37% 7% 14% 27% 13% 2	1663
	21st to end	Night	35% 7% 12% 27% 17% 1	1620
May	1st to 10th	Night	38% 8% 14% 25% 15% 1	1620
	11th to 20th	Night	36% 9% 16% 25% 14% 1	1594
	21st to end	Night	38% 9% 19% 20% 11% 3	1746
June	1st to 10th	Night	26% 8% 20% 30% 14% 2	1495
	11th to 20th	Night	29% 6% 14% 29% 17% 5%	1440
	21st to end	Night	24% 7% 17% 30% 18% 3	1440
July	1st to 10th	Night	27% 5% 18% 30% 16% 4	1400
	11th to 20th	Night	21% 8% 17% 27% 21% 5%	1392
	21st to end	Night	23% 9% 18% 31% 16% 3	1664
August	1st to 10th	Night	29% 9% 20% 27% 12% 2	1601
	11th to 20th	Night	24% 6% 18% 32% 17% 3	1600
	21st to end	Night	23% 6% 14% 26% 23% 8%	1853
September	1st to 10th	Night	24% 4 11% 25% 26% 9%	1902
	11th to 20th	Night	24% 6% 12% 32% 22% 4	1980
	21st to end	Night	25% 5% 9% 29% 29% 3	1980
October	1st to 10th	Night	33% 5% 10% 24% 24% 3	1984
	11th to 20th	Night	27% 4 9% 28% 25% 7%	2160
	21st to end	Night	31% 4 12% 24% 23% 6%	2518
November	1st to 10th	Night	21% 6% 14% 27% 26% 6%	2405
	11th to 20th	Night	29% 4 11% 28% 23% 5%	2470
	21st to end	Night	30% 4 12% 28% 22% 3	2470
December	1st to 10th	Night	32% 5% 14% 28% 17% 3	2470
	11th to 20th	Night	30% 5% 14% 35% 16% 1	3103
	21st to end	Night	46% 5% 12% 26% 10% 1	4873

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	15% 13% 33% 27% 9% 3	270
	11th to 20th	Day	16% 12% 35% 27% 10%	246
	21st to end	Day	12% 11% 46% 23% 7%	264
February	1st to 10th	Day	12% 13% 46% 25% 5%	240
	11th to 20th	Day	13% 12% 45% 22% 7% 1	240
	21st to end	Day	18% 18% 42% 19% 4	198
March	1st to 10th	Day	12% 13% 38% 32% 5% 1	240
	11th to 20th	Day	20% 7% 38% 27% 7%	240
	21st to end	Day	22% 15% 35% 21% 5% 1	264
April	1st to 10th	Day	16% 21% 40% 19% 4 1	346
	11th to 20th	Day	20% 17% 34% 24% 5%	526
	21st to end	Day	21% 13% 32% 23% 10% 2	600
May	1st to 10th	Day	15% 12% 34% 30% 7% 1	603
	11th to 20th	Day	19% 11% 32% 22% 14% 3	625
	21st to end	Day	15% 9% 32% 29% 13% 1	679
June	1st to 10th	Day	7% 6% 26% 35% 20% 6%	630
	11th to 20th	Day	10% 6% 32% 37% 13% 2	630
	21st to end	Day	6% 8% 29% 40% 16% 2	630
July	1st to 10th	Day	7% 2 21% 39% 27% 4	621
	11th to 20th	Day	3 2 22% 44% 24% 3	618
	21st to end	Day	7% 4 19% 45% 23% 2	684
August	1st to 10th	Day	9% 2 21% 43% 23% 3	626
	11th to 20th	Day	7% 4 23% 42% 22% 2	615
	21st to end	Day	9% 3 24% 39% 21% 4	619
September	1st to 10th	Day	11% 6% 32% 32% 17% 3	347
	11th to 20th	Day	7% 6% 31% 34% 17% 5%	270
	21st to end	Day	14% 10% 28% 32% 13% 3	270
October	1st to 10th	Day	21% 8% 23% 30% 13% 5%	270
	11th to 20th	Day	11% 14% 37% 26% 9% 2	270
	21st to end	Day	20% 14% 33% 25% 7% 1	297
November	1st to 10th	Day	12% 14% 40% 21% 10% 3	270
	11th to 20th	Day	10% 14% 45% 23% 7% 1	270
	21st to end	Day	18% 13% 36% 21% 10% 2	270
December	1st to 10th	Day	9% 9% 48% 26% 8% 1	270
	11th to 20th	Day	15% 13% 36% 26% 9% 1	270
	21st to end	Day	21% 13% 39% 24% 2 1	297
January	1st to 10th	Night	12% 11% 36% 34% 7%	950
	11th to 20th	Night	11% 13% 37% 31% 7% 1	911
	21st to end	Night	12% 10% 43% 29% 6%	990
February	1st to 10th	Night	13% 11% 42% 29% 5%	900
	11th to 20th	Night	10% 11% 46% 29% 4 1	722
	21st to end	Night	11% 11% 41% 32% 6%	592
March	1st to 10th	Night	11% 11% 45% 28% 5%	689
	11th to 20th	Night	15% 10% 39% 30% 6%	540
	21st to end	Night	20% 9% 41% 24% 6%	594
April	1st to 10th	Night	17% 12% 44% 25% 2	540
	11th to 20th	Night	17% 13% 41% 27% 3	533
	21st to end	Night	17% 10% 33% 31% 9%	540
May	1st to 10th	Night	14% 8% 38% 33% 7%	540
	11th to 20th	Night	14% 8% 38% 31% 8% 1	531
	21st to end	Night	16% 7% 31% 33% 11% 1	584
June	1st to 10th	Night	8% 5% 26% 46% 12% 2	540
	11th to 20th	Night	12% 4 35% 37% 12%	540
	21st to end	Night	3 6% 29% 49% 13%	540
July	1st to 10th	Night	6% 3 21% 46% 23% 1	525
	11th to 20th	Night	4 2 21% 54% 18% 1	522
	21st to end	Night	5% 2 19% 57% 16%	591
August	1st to 10th	Night	7% 2 20% 51% 20% 1	537
	11th to 20th	Night	7% 2 24% 47% 19%	534
	21st to end	Night	8% 1 27% 46% 18% 1	594
September	1st to 10th	Night	10% 3 28% 44% 14% 2	540
	11th to 20th	Night	8% 4 32% 39% 15% 1	540
	21st to end	Night	9% 7% 35% 35% 13% 1	540
October	1st to 10th	Night	18% 6% 32% 30% 12%	544
	11th to 20th	Night	13% 13% 34% 30% 9%	720
	21st to end	Night	15% 11% 32% 31% 10%	934
November	1st to 10th	Night	8% 10% 37% 38% 7% 1	925
	11th to 20th	Night	11% 11% 39% 31% 8%	950
	21st to end	Night	10% 11% 36% 32% 10% 1	950
December	1st to 10th	Night	11% 11% 43% 30% 5%	950
	11th to 20th	Night	12% 10% 39% 31% 8%	950
	21st to end	Night	16% 12% 36% 29% 5%	1045

Page generated at 2024-01-10 00:25:01. Version ac07

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