Deerwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deerwood clear sky chart from 2005-11-06 to 2026-07-01.

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% 8% 3 8% 6% 5% 5% 4 6% 8% 36%	141945
	Night	8% 9% 3 9% 6% 5% 5% 4 6% 8% 36%	139256
Transparency	Day	44% 7% 16% 24% 9% 1	141652
	Night	44% 7% 15% 23% 10% 1	139134
Seeing	Day	14% 11% 33% 28% 12% 3	18522
	Night	13% 10% 34% 31% 10% 1	28466

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	4 12% 5% 13% 7% 9% 8% 5% 7% 7% 22%	4125
	11th to 20th	Day	4 8% 3 12% 8% 8% 10% 9% 12% 9% 15%	4376
	21st to end	Day	4 8% 3 10% 6% 7% 9% 4 8% 10% 30%	5188
February	1st to 10th	Day	8% 11% 4 11% 9% 6% 5% 5% 7% 10% 24%	1752
	11th to 20th	Day	6% 9% 3 10% 9% 8% 7% 6% 9% 8% 26%	1844
	21st to end	Day	6% 10% 5% 11% 7% 7% 6% 7% 7% 7% 26%	1710
March	1st to 10th	Day	8% 11% 3 10% 6% 6% 5% 4 7% 10% 31%	4615
	11th to 20th	Day	8% 11% 5% 11% 10% 6% 5% 4 6% 9% 24%	5088
	21st to end	Day	8% 13% 5% 15% 7% 5% 5% 4 6% 6% 25%	5585
April	1st to 10th	Day	8% 13% 5% 8% 6% 4 5% 4 5% 7% 36%	2566
	11th to 20th	Day	13% 12% 4 10% 6% 5% 5% 4 5% 6% 30%	2702
	21st to end	Day	16% 10% 4 8% 5% 4 4 4 5% 6% 33%	2730
May	1st to 10th	Day	11% 9% 3 6% 4 3 4 3 6% 7% 44%	7655
	11th to 20th	Day	18% 11% 3 7% 4 4 4 4 6% 7% 31%	8759
	21st to end	Day	12% 7% 3 6% 5% 5% 4 4 5% 7% 43%	9683
June	1st to 10th	Day	12% 7% 2 6% 5% 5% 5% 5% 7% 9% 37%	3150
	11th to 20th	Day	13% 5% 2 7% 5% 6% 5% 5% 7% 9% 35%	3150
	21st to end	Day	12% 6% 2 6% 5% 5% 6% 5% 7% 9% 35%	3150
July	1st to 10th	Day	8% 4 2 6% 5% 6% 6% 5% 8% 10% 42%	6801
	11th to 20th	Day	10% 5% 2 6% 4 5% 5% 4 6% 9% 43%	6800
	21st to end	Day	8% 5% 2 6% 4 5% 5% 4 7% 9% 44%	7089
August	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 8% 44%	4467
	11th to 20th	Day	11% 5% 2 6% 3 4 4 3 6% 9% 47%	4171
	21st to end	Day	10% 5% 2 5% 4 4 4 4 6% 8% 48%	4675
September	1st to 10th	Day	11% 6% 2 5% 4 4 4 3 5% 7% 50%	2451
	11th to 20th	Day	16% 7% 3 6% 5% 4 4 4 4 6% 42%	2200
	21st to end	Day	14% 6% 2 5% 4 4 4 3 6% 8% 44%	2200
October	1st to 10th	Day	10% 6% 2 6% 4 4 4 3 5% 6% 50%	3399
	11th to 20th	Day	9% 9% 3 7% 5% 5% 5% 4 6% 8% 39%	3091
	21st to end	Day	12% 12% 3 8% 4 5% 4 4 6% 8% 33%	3190
November	1st to 10th	Day	15% 13% 4 10% 5% 5% 4 3 5% 7% 29%	1752
	11th to 20th	Day	9% 12% 5% 14% 6% 5% 5% 4 5% 6% 29%	1680
	21st to end	Day	10% 13% 5% 11% 8% 7% 5% 3 6% 7% 26%	1507
December	1st to 10th	Day	9% 11% 6% 14% 10% 10% 7% 5% 6% 6% 17%	2360
	11th to 20th	Day	8% 12% 4 12% 7% 7% 6% 5% 7% 6% 26%	2709
	21st to end	Day	6% 9% 4 13% 8% 7% 6% 5% 6% 6% 31%	3575
January	1st to 10th	Night	4 10% 6% 15% 9% 7% 7% 5% 7% 7% 22%	8799
	11th to 20th	Night	4 10% 5% 12% 7% 7% 9% 8% 9% 9% 22%	8535
	21st to end	Night	5% 10% 5% 11% 6% 6% 6% 5% 8% 8% 30%	9026
February	1st to 10th	Night	7% 12% 4 10% 7% 7% 6% 5% 8% 7% 27%	2867
	11th to 20th	Night	6% 9% 3 8% 7% 6% 7% 5% 7% 10% 34%	2663
	21st to end	Night	6% 10% 4 9% 6% 7% 6% 4 7% 8% 33%	2113
March	1st to 10th	Night	7% 10% 3 9% 6% 5% 5% 5% 7% 8% 34%	5477
	11th to 20th	Night	6% 10% 4 10% 8% 5% 5% 4 6% 7% 33%	5090
	21st to end	Night	9% 11% 5% 14% 7% 5% 4 4 5% 5% 31%	5588
April	1st to 10th	Night	8% 8% 4 8% 6% 4 5% 4 7% 7% 41%	2051
	11th to 20th	Night	13% 11% 5% 9% 6% 4 6% 4 6% 6% 32%	1869
	21st to end	Night	12% 10% 4 7% 6% 4 5% 4 7% 7% 35%	1890
May	1st to 10th	Night	13% 6% 2 6% 5% 5% 4 4 6% 7% 42%	5293
	11th to 20th	Night	16% 8% 2 6% 4 4 4 4 6% 7% 39%	4129
	21st to end	Night	13% 6% 2 5% 3 3 4 3 5% 6% 51%	4523
June	1st to 10th	Night	10% 6% 2 6% 5% 4 5% 4 6% 8% 45%	1470
	11th to 20th	Night	11% 6% 1 7% 4 5% 4 4 7% 7% 44%	1470
	21st to end	Night	11% 5% 2 5% 4 5% 4 4 6% 9% 44%	1470
July	1st to 10th	Night	7% 3 1 4 3 3 4 4 7% 10% 52%	3180
	11th to 20th	Night	7% 4 1 4 4 4 4 4 6% 9% 54%	3180
	21st to end	Night	5% 5% 2 5% 4 4 5% 4 7% 9% 49%	3775
August	1st to 10th	Night	5% 5% 2 6% 4 4 4 4 6% 8% 51%	2693
	11th to 20th	Night	9% 3 1 6% 3 4 5% 3 6% 10% 50%	2888
	21st to end	Night	9% 4 2 5% 4 4 4 3 5% 7% 53%	3234
September	1st to 10th	Night	9% 5% 2 4 3 3 4 3 5% 9% 54%	1945
	11th to 20th	Night	13% 5% 2 5% 3 4 4 4 5% 7% 48%	2200
	21st to end	Night	14% 6% 2 6% 4 4 4 4 5% 6% 46%	2200
October	1st to 10th	Night	10% 6% 2 5% 4 4 4 4 5% 8% 48%	3747
	11th to 20th	Night	9% 9% 2 7% 4 4 4 4 5% 8% 43%	4052
	21st to end	Night	8% 9% 3 9% 5% 4 5% 4 6% 7% 41%	4610
November	1st to 10th	Night	12% 11% 4 9% 5% 4 5% 4 6% 7% 32%	2765
	11th to 20th	Night	9% 14% 5% 11% 6% 5% 6% 4 6% 6% 29%	2940
	21st to end	Night	9% 13% 5% 11% 7% 6% 4 4 6% 7% 29%	3111
December	1st to 10th	Night	7% 11% 4 13% 11% 10% 7% 5% 6% 7% 20%	5050
	11th to 20th	Night	7% 13% 5% 13% 8% 8% 6% 4 6% 7% 24%	5718
	21st to end	Night	7% 9% 3 12% 9% 7% 6% 4 6% 7% 30%	7645

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	58% 6% 12% 18% 7%	4125
	11th to 20th	Day	57% 6% 12% 17% 7%	4398
	21st to end	Day	47% 5% 15% 23% 10%	5188
February	1st to 10th	Day	54% 6% 13% 17% 8% 1	1752
	11th to 20th	Day	50% 9% 12% 19% 10%	1853
	21st to end	Day	52% 9% 13% 16% 8%	1710
March	1st to 10th	Day	45% 8% 20% 17% 10%	4615
	11th to 20th	Day	54% 8% 15% 17% 6%	5090
	21st to end	Day	56% 8% 11% 19% 6%	5585
April	1st to 10th	Day	47% 7% 14% 22% 9% 1	2566
	11th to 20th	Day	52% 8% 12% 18% 10% 1	2702
	21st to end	Day	49% 7% 16% 18% 8% 1	2730
May	1st to 10th	Day	36% 5% 13% 29% 15% 1	7655
	11th to 20th	Day	49% 7% 11% 23% 9% 2	8763
	21st to end	Day	38% 6% 10% 24% 20% 2	9683
June	1st to 10th	Day	40% 8% 18% 23% 10% 1	3150
	11th to 20th	Day	41% 10% 17% 22% 9% 1	3150
	21st to end	Day	40% 10% 20% 23% 5% 1	3150
July	1st to 10th	Day	34% 8% 27% 27% 5%	6727
	11th to 20th	Day	35% 7% 20% 32% 5%	6719
	21st to end	Day	33% 7% 24% 28% 8%	6891
August	1st to 10th	Day	35% 8% 18% 27% 13%	4451
	11th to 20th	Day	34% 6% 20% 33% 6%	4210
	21st to end	Day	32% 5% 22% 31% 9%	4674
September	1st to 10th	Day	33% 6% 19% 30% 11% 1	2451
	11th to 20th	Day	43% 7% 17% 23% 9% 1	2200
	21st to end	Day	37% 7% 16% 30% 10%	2200
October	1st to 10th	Day	35% 5% 13% 35% 12% 1	3399
	11th to 20th	Day	42% 6% 12% 27% 13%	3091
	21st to end	Day	48% 6% 13% 24% 9%	3190
November	1st to 10th	Day	54% 8% 10% 19% 8% 1	1752
	11th to 20th	Day	56% 6% 16% 14% 6% 1	1680
	21st to end	Day	57% 8% 14% 16% 5%	1507
December	1st to 10th	Day	63% 8% 14% 11% 4	2360
	11th to 20th	Day	55% 8% 14% 14% 9% 1	2710
	21st to end	Day	51% 6% 11% 21% 11%	3575
January	1st to 10th	Night	57% 6% 13% 16% 7%	8800
	11th to 20th	Night	56% 6% 11% 21% 6%	8575
	21st to end	Night	48% 7% 12% 23% 10%	9026
February	1st to 10th	Night	52% 7% 13% 17% 10% 1	2867
	11th to 20th	Night	42% 9% 14% 22% 12% 1	2664
	21st to end	Night	47% 7% 13% 22% 11% 1	2113
March	1st to 10th	Night	42% 8% 18% 19% 10% 2	5477
	11th to 20th	Night	45% 8% 13% 21% 12% 1	5090
	21st to end	Night	52% 8% 10% 21% 9%	5588
April	1st to 10th	Night	39% 7% 14% 24% 14% 2	2051
	11th to 20th	Night	50% 7% 11% 19% 12% 2	1869
	21st to end	Night	46% 7% 13% 20% 12% 2	1890
May	1st to 10th	Night	39% 6% 11% 28% 16% 1	5293
	11th to 20th	Night	42% 6% 13% 24% 13% 2	4129
	21st to end	Night	33% 6% 11% 24% 23% 3	4526
June	1st to 10th	Night	35% 9% 19% 26% 10% 2	1470
	11th to 20th	Night	36% 8% 17% 25% 12% 2	1470
	21st to end	Night	34% 11% 21% 27% 6% 1	1470
July	1st to 10th	Night	26% 6% 29% 31% 6% 1	3145
	11th to 20th	Night	27% 6% 20% 39% 8% 1	3138
	21st to end	Night	29% 6% 26% 30% 8% 1	3668
August	1st to 10th	Night	29% 6% 18% 32% 15% 1	2685
	11th to 20th	Night	29% 6% 23% 32% 9% 1	2915
	21st to end	Night	30% 5% 20% 34% 11% 1	3234
September	1st to 10th	Night	28% 7% 15% 34% 14% 2	1945
	11th to 20th	Night	34% 8% 20% 26% 12% 1	2200
	21st to end	Night	37% 7% 12% 30% 12% 1	2200
October	1st to 10th	Night	34% 6% 14% 30% 15% 1	3747
	11th to 20th	Night	38% 5% 12% 29% 15% 1	4052
	21st to end	Night	41% 6% 14% 31% 8%	4610
November	1st to 10th	Night	48% 9% 15% 17% 8% 2	2765
	11th to 20th	Night	54% 8% 14% 15% 8% 1	2940
	21st to end	Night	54% 8% 15% 16% 6%	3111
December	1st to 10th	Night	62% 8% 14% 12% 4	5050
	11th to 20th	Night	58% 7% 12% 15% 7%	5716
	21st to end	Night	51% 6% 13% 20% 10% 1	7645

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	8% 12% 37% 32% 10% 1	330
	11th to 20th	Day	12% 12% 43% 25% 8% 1	330
	21st to end	Day	13% 12% 42% 22% 9% 1	363
February	1st to 10th	Day	13% 15% 40% 25% 5% 2	330
	11th to 20th	Day	9% 16% 33% 33% 7% 1	330
	21st to end	Day	8% 8% 46% 30% 7% 1	273
March	1st to 10th	Day	13% 13% 35% 30% 9% 1	330
	11th to 20th	Day	16% 11% 35% 28% 8% 2	330
	21st to end	Day	12% 18% 31% 29% 7% 3	363
April	1st to 10th	Day	14% 17% 34% 24% 10% 1	586
	11th to 20th	Day	19% 13% 34% 24% 10% 1	740
	21st to end	Day	17% 12% 34% 25% 10% 2	750
May	1st to 10th	Day	15% 11% 33% 28% 10% 3	753
	11th to 20th	Day	21% 11% 31% 24% 11% 2	775
	21st to end	Day	18% 9% 24% 29% 15% 4	844
June	1st to 10th	Day	13% 14% 31% 24% 13% 5%	780
	11th to 20th	Day	14% 12% 36% 24% 12% 2	780
	21st to end	Day	14% 9% 28% 32% 14% 3	780
July	1st to 10th	Day	7% 6% 28% 32% 18% 8%	722
	11th to 20th	Day	11% 8% 31% 28% 18% 4	718
	21st to end	Day	5% 5% 30% 36% 18% 7%	794
August	1st to 10th	Day	8% 6% 29% 30% 21% 6%	726
	11th to 20th	Day	10% 5% 26% 32% 18% 8%	715
	21st to end	Day	11% 7% 29% 33% 17% 4	803
September	1st to 10th	Day	11% 10% 35% 29% 12% 3	581
	11th to 20th	Day	21% 11% 31% 25% 12% 1	330
	21st to end	Day	20% 10% 30% 27% 10% 2	330
October	1st to 10th	Day	18% 16% 27% 27% 12% 1	330
	11th to 20th	Day	17% 11% 43% 23% 5% 2	330
	21st to end	Day	20% 14% 36% 21% 7% 2	363
November	1st to 10th	Day	24% 13% 30% 25% 8%	330
	11th to 20th	Day	14% 20% 35% 25% 7%	330
	21st to end	Day	15% 16% 39% 25% 5%	330
December	1st to 10th	Day	13% 13% 38% 25% 9% 2	330
	11th to 20th	Day	17% 17% 39% 22% 4 1	330
	21st to end	Day	13% 11% 39% 27% 8% 3	363
January	1st to 10th	Night	11% 13% 35% 30% 10% 1	1050
	11th to 20th	Night	14% 13% 39% 29% 5%	1050
	21st to end	Night	12% 14% 40% 28% 6% 1	1155
February	1st to 10th	Night	12% 13% 36% 30% 8% 1	1050
	11th to 20th	Night	10% 11% 36% 33% 9% 1	1029
	21st to end	Night	11% 11% 38% 30% 9% 2	729
March	1st to 10th	Night	14% 12% 34% 27% 11% 2	836
	11th to 20th	Night	9% 11% 42% 27% 10% 1	630
	21st to end	Night	15% 10% 30% 31% 10% 3	693
April	1st to 10th	Night	11% 9% 37% 33% 9% 1	630
	11th to 20th	Night	17% 8% 36% 30% 9%	623
	21st to end	Night	17% 8% 29% 36% 10% 1	630
May	1st to 10th	Night	16% 7% 34% 33% 9% 1	630
	11th to 20th	Night	18% 9% 29% 32% 13%	621
	21st to end	Night	18% 8% 30% 32% 12%	683
June	1st to 10th	Night	12% 8% 30% 37% 11% 1	630
	11th to 20th	Night	14% 5% 34% 33% 14%	630
	21st to end	Night	11% 6% 28% 38% 16%	630
July	1st to 10th	Night	6% 4 25% 42% 22% 2	585
	11th to 20th	Night	7% 4 29% 41% 18% 1	582
	21st to end	Night	5% 4 26% 43% 19% 2	657
August	1st to 10th	Night	8% 4 24% 43% 20% 1	597
	11th to 20th	Night	10% 4 25% 39% 19% 3	594
	21st to end	Night	8% 6% 28% 39% 18% 1	660
September	1st to 10th	Night	10% 5% 32% 36% 16% 2	600
	11th to 20th	Night	14% 8% 30% 37% 11% 1	600
	21st to end	Night	17% 7% 34% 29% 14%	600
October	1st to 10th	Night	19% 11% 33% 30% 7%	692
	11th to 20th	Night	19% 12% 34% 28% 8%	890
	21st to end	Night	16% 12% 37% 26% 8% 1	1100
November	1st to 10th	Night	16% 13% 36% 26% 8% 1	1025
	11th to 20th	Night	14% 15% 38% 24% 7% 2	1050
	21st to end	Night	15% 16% 40% 23% 5% 1	1050
December	1st to 10th	Night	10% 13% 39% 29% 8% 1	1050
	11th to 20th	Night	15% 13% 38% 26% 7% 1	1050
	21st to end	Night	18% 8% 35% 29% 8% 1	1155

Page generated at 2026-06-28 01:10:48. Version ac07

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