Apgar Village
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Apgar Village clear sky chart from 2005-11-06 to 2026-08-30.

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% 12% 4 8% 4 4 4 3 5% 6% 38%	148212
	Night	11% 15% 4 9% 5% 4 4 3 5% 6% 34%	142732
Transparency	Day	46% 7% 14% 20% 10% 3	147927
	Night	51% 7% 15% 17% 8% 2	142600
Seeing	Day	22% 18% 28% 21% 9% 2	17660
	Night	24% 11% 27% 28% 9% 1	26740

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	8% 30% 11% 22% 7% 5% 4 3 3 3 5%	4125
	11th to 20th	Day	10% 16% 5% 14% 4 4 6% 4 5% 5% 28%	4632
	21st to end	Day	11% 21% 5% 12% 5% 6% 4 3 4 5% 23%	5186
February	1st to 10th	Day	18% 24% 8% 12% 7% 4 3 2 3 4 16%	1750
	11th to 20th	Day	11% 25% 7% 13% 5% 4 4 3 5% 5% 17%	1856
	21st to end	Day	10% 28% 9% 15% 5% 4 3 2 3 3 18%	1730
March	1st to 10th	Day	7% 18% 5% 10% 5% 4 4 3 5% 8% 32%	4618
	11th to 20th	Day	9% 21% 6% 10% 5% 4 4 3 4 5% 30%	5081
	21st to end	Day	11% 24% 6% 11% 7% 6% 5% 4 4 5% 17%	5644
April	1st to 10th	Day	11% 18% 5% 11% 6% 5% 5% 5% 6% 6% 22%	2543
	11th to 20th	Day	14% 17% 5% 9% 6% 5% 5% 4 5% 5% 24%	2700
	21st to end	Day	12% 16% 5% 10% 5% 5% 5% 4 6% 6% 26%	2730
May	1st to 10th	Day	11% 9% 3 6% 4 4 4 3 5% 7% 42%	7626
	11th to 20th	Day	9% 10% 3 11% 7% 7% 7% 5% 7% 8% 24%	8475
	21st to end	Day	14% 8% 2 6% 4 5% 6% 4 6% 9% 35%	9649
June	1st to 10th	Day	20% 8% 3 8% 5% 5% 5% 4 6% 6% 29%	3150
	11th to 20th	Day	20% 8% 3 7% 6% 5% 5% 5% 6% 7% 28%	3150
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 7% 8% 43%	3150
July	1st to 10th	Day	4 2 1 3 3 3 4 3 5% 7% 64%	8820
	11th to 20th	Day	5% 3 1 4 2 3 3 2 4 6% 67%	8785
	21st to end	Day	3 2 1 3 2 2 2 2 4 7% 73%	8916
August	1st to 10th	Day	6% 3 1 4 2 3 4 4 7% 8% 57%	4590
	11th to 20th	Day	5% 3 1 4 3 4 4 3 6% 8% 59%	4288
	21st to end	Day	7% 4 2 4 3 4 4 3 5% 6% 59%	4782
September	1st to 10th	Day	8% 5% 2 6% 3 3 4 4 5% 7% 54%	2415
	11th to 20th	Day	11% 6% 3 7% 5% 4 4 4 5% 7% 44%	2200
	21st to end	Day	13% 6% 2 7% 4 3 4 4 5% 7% 44%	2200
October	1st to 10th	Day	9% 6% 2 4 3 4 4 3 4 6% 54%	3483
	11th to 20th	Day	12% 8% 3 6% 4 3 4 4 6% 8% 40%	3072
	21st to end	Day	15% 17% 5% 10% 4 4 4 4 6% 7% 23%	3200
November	1st to 10th	Day	22% 21% 6% 10% 5% 4 3 3 5% 5% 16%	1822
	11th to 20th	Day	19% 23% 6% 11% 4 4 3 3 4 5% 19%	1680
	21st to end	Day	15% 25% 6% 12% 6% 4 4 3 4 6% 14%	1517
December	1st to 10th	Day	10% 17% 6% 13% 6% 4 4 3 4 5% 28%	2360
	11th to 20th	Day	14% 23% 8% 14% 6% 4 4 4 4 4 15%	2712
	21st to end	Day	11% 26% 10% 16% 6% 5% 4 3 4 5% 10%	3575
January	1st to 10th	Night	10% 30% 10% 18% 7% 5% 4 2 3 3 8%	8768
	11th to 20th	Night	9% 13% 6% 13% 5% 4 4 3 4 5% 32%	8324
	21st to end	Night	11% 22% 4 10% 5% 5% 5% 4 5% 6% 22%	8994
February	1st to 10th	Night	16% 25% 6% 10% 5% 4 3 3 4 5% 17%	2868
	11th to 20th	Night	12% 25% 7% 12% 6% 3 3 2 3 4 21%	2647
	21st to end	Night	9% 27% 7% 13% 6% 4 3 3 4 5% 18%	2076
March	1st to 10th	Night	8% 17% 6% 10% 5% 3 4 3 5% 7% 33%	5496
	11th to 20th	Night	10% 15% 4 9% 5% 5% 5% 4 5% 5% 34%	5138
	21st to end	Night	14% 25% 5% 10% 6% 5% 5% 4 4 5% 17%	5571
April	1st to 10th	Night	11% 19% 4 7% 6% 4 4 3 5% 6% 31%	2076
	11th to 20th	Night	13% 15% 5% 9% 6% 4 4 5% 3 6% 30%	1871
	21st to end	Night	12% 15% 3 7% 5% 4 5% 4 6% 6% 33%	1890
May	1st to 10th	Night	12% 9% 2 6% 4 4 4 3 6% 8% 42%	5322
	11th to 20th	Night	13% 11% 3 8% 5% 5% 5% 4 5% 8% 32%	4368
	21st to end	Night	15% 8% 2 7% 5% 4 4 4 6% 7% 37%	4522
June	1st to 10th	Night	20% 7% 3 6% 4 4 4 4 5% 7% 37%	1470
	11th to 20th	Night	20% 6% 2 6% 5% 5% 5% 6% 6% 6% 33%	1470
	21st to end	Night	8% 5% 1 6% 4 4 4 4 5% 7% 53%	1470
July	1st to 10th	Night	4 2 1 4 2 3 3 3 4 6% 68%	4140
	11th to 20th	Night	4 2 1 3 3 2 4 2 4 5% 70%	4158
	21st to end	Night	3 2 1 4 2 2 2 2 4 6% 72%	5152
August	1st to 10th	Night	4 3 2 4 2 3 3 3 4 8% 65%	2781
	11th to 20th	Night	4 3 2 4 3 3 5% 4 7% 10% 55%	2991
	21st to end	Night	5% 2 1 3 3 3 3 3 5% 8% 63%	3326
September	1st to 10th	Night	6% 4 2 4 3 4 4 4 5% 6% 58%	1981
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 6% 8% 50%	2200
	21st to end	Night	13% 6% 2 4 2 3 3 4 5% 8% 50%	2200
October	1st to 10th	Night	9% 7% 2 6% 3 3 4 3 4 6% 53%	3712
	11th to 20th	Night	10% 7% 2 4 3 4 4 3 5% 8% 50%	4073
	21st to end	Night	11% 12% 3 8% 5% 4 4 3 5% 6% 37%	4600
November	1st to 10th	Night	22% 20% 4 7% 5% 4 4 4 4 5% 21%	2675
	11th to 20th	Night	19% 24% 4 8% 4 4 3 3 4 4 21%	2940
	21st to end	Night	17% 24% 5% 11% 6% 4 3 2 4 5% 19%	3099
December	1st to 10th	Night	10% 19% 6% 9% 5% 4 4 3 4 5% 31%	5040
	11th to 20th	Night	12% 24% 7% 14% 7% 5% 4 3 4 6% 13%	5700
	21st to end	Night	11% 24% 8% 15% 7% 6% 5% 3 5% 5% 10%	7623

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	82% 6% 9% 2 1	4125
	11th to 20th	Day	58% 6% 18% 10% 7% 1	4656
	21st to end	Day	62% 7% 17% 11% 3	5187
February	1st to 10th	Day	75% 8% 8% 6% 3 1	1750
	11th to 20th	Day	70% 9% 11% 7% 4	1865
	21st to end	Day	73% 7% 8% 8% 4 1	1730
March	1st to 10th	Day	51% 9% 16% 15% 10%	4618
	11th to 20th	Day	56% 8% 21% 13% 2	5082
	21st to end	Day	68% 8% 12% 9% 3	5644
April	1st to 10th	Day	62% 9% 15% 13% 1	2543
	11th to 20th	Day	61% 10% 13% 13% 3	2700
	21st to end	Day	57% 10% 13% 16% 3 1	2730
May	1st to 10th	Day	41% 6% 15% 28% 10%	7626
	11th to 20th	Day	51% 10% 18% 16% 5%	8479
	21st to end	Day	43% 10% 20% 22% 4	9650
June	1st to 10th	Day	55% 9% 14% 16% 6%	3150
	11th to 20th	Day	54% 8% 13% 15% 8% 1	3150
	21st to end	Day	37% 10% 17% 24% 11% 1	3150
July	1st to 10th	Day	20% 4 11% 32% 24% 8%	8746
	11th to 20th	Day	20% 3 10% 25% 23% 18%	8704
	21st to end	Day	14% 2 8% 30% 31% 14%	8723
August	1st to 10th	Day	23% 6% 13% 30% 21% 7%	4573
	11th to 20th	Day	23% 5% 16% 37% 17% 2	4327
	21st to end	Day	26% 6% 13% 35% 18% 3	4781
September	1st to 10th	Day	30% 8% 12% 27% 18% 5%	2415
	11th to 20th	Day	39% 9% 13% 24% 14% 2	2200
	21st to end	Day	40% 9% 18% 22% 10% 1	2200
October	1st to 10th	Day	30% 7% 21% 33% 10%	3483
	11th to 20th	Day	42% 8% 22% 21% 7%	3072
	21st to end	Day	58% 7% 18% 14% 2	3200
November	1st to 10th	Day	71% 8% 11% 7% 2	1822
	11th to 20th	Day	68% 9% 13% 6% 4	1680
	21st to end	Day	70% 12% 9% 6% 3	1517
December	1st to 10th	Day	59% 11% 19% 9% 1	2360
	11th to 20th	Day	72% 7% 17% 4 1	2714
	21st to end	Day	72% 7% 14% 6% 1	3575
January	1st to 10th	Night	81% 5% 8% 5% 1	8769
	11th to 20th	Night	54% 7% 19% 9% 8% 3	8362
	21st to end	Night	61% 8% 18% 10% 2	8994
February	1st to 10th	Night	71% 8% 7% 8% 4 1	2868
	11th to 20th	Night	70% 7% 9% 8% 4	2648
	21st to end	Night	71% 7% 8% 11% 3 1	2076
March	1st to 10th	Night	50% 8% 16% 14% 11%	5496
	11th to 20th	Night	50% 7% 19% 21% 2	5138
	21st to end	Night	67% 9% 11% 10% 1	5571
April	1st to 10th	Night	54% 10% 18% 15% 3	2076
	11th to 20th	Night	57% 9% 13% 16% 5%	1871
	21st to end	Night	51% 10% 14% 19% 5% 1	1890
May	1st to 10th	Night	41% 7% 17% 26% 10%	5319
	11th to 20th	Night	49% 8% 15% 23% 6%	4368
	21st to end	Night	43% 11% 20% 23% 4	4526
June	1st to 10th	Night	47% 10% 17% 19% 7%	1470
	11th to 20th	Night	50% 10% 11% 19% 8% 1	1470
	21st to end	Night	32% 8% 19% 26% 14% 1	1470
July	1st to 10th	Night	18% 4 13% 30% 25% 10%	4105
	11th to 20th	Night	18% 3 9% 26% 23% 20%	4116
	21st to end	Night	17% 2 10% 26% 25% 20%	5040
August	1st to 10th	Night	19% 5% 14% 31% 23% 9%	2773
	11th to 20th	Night	22% 6% 19% 36% 15% 3	3018
	21st to end	Night	21% 5% 13% 36% 22% 3	3326
September	1st to 10th	Night	24% 9% 16% 28% 17% 6%	1981
	11th to 20th	Night	32% 10% 15% 28% 14% 2	2200
	21st to end	Night	34% 9% 18% 24% 13% 2	2200
October	1st to 10th	Night	32% 7% 18% 31% 11%	3712
	11th to 20th	Night	33% 7% 23% 25% 10%	4073
	21st to end	Night	48% 6% 24% 18% 5%	4600
November	1st to 10th	Night	65% 9% 13% 9% 4 1	2675
	11th to 20th	Night	67% 10% 12% 7% 4	2940
	21st to end	Night	69% 9% 11% 8% 3	3099
December	1st to 10th	Night	56% 11% 20% 11% 2	5040
	11th to 20th	Night	73% 9% 13% 4 1	5697
	21st to end	Night	71% 9% 13% 5% 2	7623

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	28% 17% 27% 15% 10% 2	220
	11th to 20th	Day	32% 16% 27% 16% 9%	220
	21st to end	Day	22% 19% 37% 16% 6%	242
February	1st to 10th	Day	28% 21% 36% 12% 3	258
	11th to 20th	Day	24% 22% 26% 22% 7%	341
	21st to end	Day	33% 22% 30% 12% 3	446
March	1st to 10th	Day	33% 21% 25% 15% 5% 1	540
	11th to 20th	Day	27% 21% 27% 16% 8% 2	540
	21st to end	Day	32% 22% 28% 12% 5% 1	594
April	1st to 10th	Day	26% 21% 31% 16% 4 1	540
	11th to 20th	Day	29% 23% 27% 15% 6%	532
	21st to end	Day	22% 20% 31% 18% 7% 2	540
May	1st to 10th	Day	18% 18% 27% 25% 9% 3	543
	11th to 20th	Day	23% 15% 26% 23% 11% 2	692
	21st to end	Day	25% 12% 22% 22% 16% 3	844
June	1st to 10th	Day	23% 15% 26% 23% 11% 3	780
	11th to 20th	Day	26% 19% 24% 21% 9% 1	780
	21st to end	Day	15% 14% 28% 27% 14% 2	780
July	1st to 10th	Day	9% 11% 28% 33% 16% 3	771
	11th to 20th	Day	9% 15% 31% 30% 13% 1	759
	21st to end	Day	5% 19% 33% 30% 11% 2	619
August	1st to 10th	Day	10% 14% 35% 29% 11% 2	567
	11th to 20th	Day	8% 13% 37% 26% 13% 3	557
	21st to end	Day	11% 17% 33% 26% 10% 2	620
September	1st to 10th	Day	14% 18% 30% 23% 11% 5%	530
	11th to 20th	Day	17% 22% 27% 22% 9% 2	530
	21st to end	Day	23% 23% 28% 17% 8% 2	530
October	1st to 10th	Day	20% 17% 31% 22% 9% 1	465
	11th to 20th	Day	27% 18% 23% 19% 10% 4	330
	21st to end	Day	32% 20% 21% 19% 7% 1	363
November	1st to 10th	Day	36% 17% 28% 16% 4	330
	11th to 20th	Day	33% 15% 30% 15% 7%	330
	21st to end	Day	30% 19% 29% 13% 9%	245
December	1st to 10th	Day	35% 20% 21% 12% 11% 1	220
	11th to 20th	Day	35% 14% 32% 17% 2	220
	21st to end	Day	21% 19% 31% 21% 7% 1	242
January	1st to 10th	Night	35% 15% 27% 19% 4	1050
	11th to 20th	Night	31% 12% 30% 22% 5% 1	891
	21st to end	Night	27% 11% 36% 22% 4	924
February	1st to 10th	Night	30% 13% 33% 20% 4	840
	11th to 20th	Night	28% 12% 34% 21% 5%	824
	21st to end	Night	25% 17% 30% 23% 5%	692
March	1st to 10th	Night	27% 15% 32% 21% 5% 1	840
	11th to 20th	Night	28% 13% 26% 27% 6% 1	840
	21st to end	Night	30% 12% 29% 22% 7%	924
April	1st to 10th	Night	22% 14% 29% 25% 9%	816
	11th to 20th	Night	25% 14% 30% 24% 7%	623
	21st to end	Night	23% 13% 24% 29% 9% 1	630
May	1st to 10th	Night	21% 9% 24% 35% 9% 1	630
	11th to 20th	Night	18% 7% 23% 35% 15% 2	431
	21st to end	Night	23% 10% 21% 25% 20% 1	455
June	1st to 10th	Night	24% 7% 23% 30% 14% 2	420
	11th to 20th	Night	26% 10% 24% 29% 12%	420
	21st to end	Night	12% 4 26% 39% 17% 1	420
July	1st to 10th	Night	7% 3 17% 54% 19%	410
	11th to 20th	Night	8% 4 23% 52% 13%	408
	21st to end	Night	5% 5% 20% 51% 18%	460
August	1st to 10th	Night	6% 6% 20% 48% 20%	471
	11th to 20th	Night	6% 5% 23% 43% 21% 2	624
	21st to end	Night	8% 7% 24% 41% 18% 1	687
September	1st to 10th	Night	8% 8% 26% 34% 19% 4	745
	11th to 20th	Night	12% 8% 23% 33% 21% 3	800
	21st to end	Night	19% 7% 22% 36% 14% 2	800
October	1st to 10th	Night	20% 8% 27% 34% 11% 1	800
	11th to 20th	Night	23% 8% 27% 31% 11% 1	800
	21st to end	Night	31% 11% 27% 25% 6%	880
November	1st to 10th	Night	35% 11% 29% 23% 3	830
	11th to 20th	Night	35% 15% 27% 18% 4	1050
	21st to end	Night	31% 14% 28% 23% 5%	1050
December	1st to 10th	Night	31% 12% 31% 20% 6%	1050
	11th to 20th	Night	33% 13% 32% 20% 2	1050
	21st to end	Night	33% 15% 30% 18% 4	1155

Page generated at 2026-08-27 02:07:09. Version ac07

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