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 2025-04-26.

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	11% 14% 4 9% 5% 4 4 3 5% 6% 35%	116974
	Night	11% 16% 5% 9% 5% 4 4 3 4 6% 32%	120355
Transparency	Day	49% 8% 14% 17% 9% 3	116730
	Night	53% 8% 14% 15% 7% 2	120245
Seeing	Day	22% 18% 28% 21% 9% 1	15774
	Night	25% 11% 28% 27% 9% 1	25163

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	10% 32% 12% 22% 6% 4 3 2 2 2 5%	3179
	11th to 20th	Day	12% 20% 7% 14% 4 4 5% 3 4 4 22%	3546
	21st to end	Day	14% 23% 5% 13% 4 4 3 2 4 5% 24%	4004
February	1st to 10th	Day	18% 24% 8% 11% 7% 4 3 2 3 4 15%	1666
	11th to 20th	Day	12% 26% 7% 12% 5% 4 4 3 4 5% 17%	1765
	21st to end	Day	10% 28% 9% 16% 5% 4 3 2 3 3 18%	1650
March	1st to 10th	Day	7% 18% 5% 10% 5% 4 4 3 5% 8% 31%	4518
	11th to 20th	Day	9% 21% 6% 9% 5% 4 4 3 4 5% 30%	4972
	21st to end	Day	11% 24% 6% 11% 7% 6% 5% 3 4 5% 16%	5522
April	1st to 10th	Day	12% 18% 5% 11% 6% 5% 5% 5% 5% 6% 21%	2422
	11th to 20th	Day	15% 17% 5% 9% 6% 5% 5% 4 5% 5% 24%	2570
	21st to end	Day	13% 16% 5% 10% 5% 5% 5% 4 6% 6% 26%	2537
May	1st to 10th	Day	18% 15% 4 9% 5% 5% 4 3 4 5% 27%	4110
	11th to 20th	Day	10% 11% 3 8% 6% 6% 6% 5% 7% 9% 30%	4549
	21st to end	Day	19% 13% 3 9% 5% 6% 6% 4 6% 7% 20%	5161
June	1st to 10th	Day	21% 9% 4 8% 5% 5% 4 4 6% 6% 28%	2850
	11th to 20th	Day	22% 8% 3 7% 6% 5% 5% 5% 6% 6% 26%	2850
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 4 7% 8% 45%	2850
July	1st to 10th	Day	3 2 1 4 4 5% 5% 4 6% 6% 61%	4740
	11th to 20th	Day	3 2 1 3 2 2 2 2 4 5% 76%	4719
	21st to end	Day	2 2 1 2 2 2 3 2 5% 7% 72%	4790
August	1st to 10th	Day	6% 3 1 4 2 3 4 4 7% 8% 57%	4316
	11th to 20th	Day	5% 3 1 4 3 4 4 3 6% 8% 59%	4028
	21st to end	Day	7% 4 2 4 3 4 4 3 5% 6% 59%	4521
September	1st to 10th	Day	8% 5% 2 6% 3 3 4 4 5% 7% 54%	2295
	11th to 20th	Day	11% 6% 3 7% 5% 4 4 4 5% 6% 44%	2090
	21st to end	Day	14% 7% 3 7% 4 3 4 3 5% 8% 43%	2090
October	1st to 10th	Day	9% 6% 2 4 3 4 4 3 4 7% 54%	3376
	11th to 20th	Day	13% 8% 3 6% 4 3 4 4 6% 8% 41%	2978
	21st to end	Day	16% 17% 5% 10% 5% 4 4 4 6% 7% 22%	3101
November	1st to 10th	Day	23% 21% 6% 10% 5% 3 3 3 5% 5% 16%	1734
	11th to 20th	Day	19% 23% 6% 12% 4 4 3 2 4 5% 19%	1600
	21st to end	Day	16% 25% 6% 12% 6% 4 4 3 4 6% 14%	1445
December	1st to 10th	Day	10% 17% 6% 12% 6% 4 4 3 4 5% 29%	2290
	11th to 20th	Day	14% 23% 7% 14% 6% 4 4 4 4 5% 15%	2642
	21st to end	Day	11% 26% 10% 15% 6% 5% 4 3 4 5% 10%	3498
January	1st to 10th	Night	11% 34% 11% 18% 6% 4 3 2 2 3 7%	6766
	11th to 20th	Night	10% 15% 8% 15% 6% 5% 5% 3 4 5% 24%	6396
	21st to end	Night	15% 24% 4 8% 4 4 4 4 4 6% 23%	6952
February	1st to 10th	Night	17% 26% 6% 10% 5% 4 3 3 4 5% 17%	2732
	11th to 20th	Night	13% 26% 7% 11% 6% 3 3 2 3 4 21%	2518
	21st to end	Night	10% 27% 7% 14% 6% 4 3 3 4 5% 18%	1980
March	1st to 10th	Night	8% 17% 6% 10% 5% 3 4 2 5% 7% 33%	5376
	11th to 20th	Night	10% 14% 4 8% 5% 5% 5% 4 5% 5% 34%	5027
	21st to end	Night	14% 25% 5% 10% 6% 5% 5% 3 4 5% 17%	5451
April	1st to 10th	Night	11% 19% 4 7% 6% 4 4 3 5% 6% 30%	1977
	11th to 20th	Night	13% 15% 5% 8% 6% 4 4 4 3 6% 31%	1781
	21st to end	Night	13% 15% 3 6% 5% 4 5% 4 6% 5% 33%	1759
May	1st to 10th	Night	20% 13% 2 8% 5% 4 4 3 5% 6% 29%	2860
	11th to 20th	Night	14% 11% 3 6% 4 4 4 3 6% 7% 38%	2325
	21st to end	Night	22% 14% 3 9% 5% 5% 4 4 5% 6% 24%	2414
June	1st to 10th	Night	21% 7% 2 6% 4 4 4 4 5% 7% 36%	1330
	11th to 20th	Night	22% 6% 3 6% 5% 5% 5% 6% 6% 6% 31%	1330
	21st to end	Night	8% 5% 1 5% 3 3 4 4 6% 8% 54%	1330
July	1st to 10th	Night	2 3 1 5% 3 4 4 4 5% 6% 63%	2220
	11th to 20th	Night	3 2 1 2 2 1 2 2 3 4 78%	2238
	21st to end	Night	2 2 1 3 2 2 2 2 4 5% 76%	2762
August	1st to 10th	Night	5% 3 1 4 2 2 2 3 4 8% 66%	2615
	11th to 20th	Night	4 3 2 4 3 3 5% 4 7% 10% 55%	2811
	21st to end	Night	6% 2 1 3 3 3 3 3 5% 8% 63%	3146
September	1st to 10th	Night	7% 5% 2 4 3 4 4 5% 5% 6% 58%	1882
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 6% 8% 50%	2090
	21st to end	Night	13% 6% 2 4 2 3 3 4 5% 8% 49%	2090
October	1st to 10th	Night	9% 7% 2 5% 3 3 4 3 4 6% 53%	3599
	11th to 20th	Night	10% 6% 2 4 3 4 4 3 5% 8% 50%	3948
	21st to end	Night	11% 13% 3 8% 5% 4 4 3 5% 6% 37%	4457
November	1st to 10th	Night	23% 20% 4 7% 5% 4 4 3 4 5% 20%	2544
	11th to 20th	Night	18% 25% 5% 8% 4 4 3 3 4 4 22%	2800
	21st to end	Night	18% 24% 5% 11% 6% 4 3 2 3 5% 19%	2951
December	1st to 10th	Night	10% 19% 6% 8% 4 4 4 3 4 6% 32%	4890
	11th to 20th	Night	11% 25% 8% 14% 7% 5% 4 3 4 6% 13%	5550
	21st to end	Night	11% 25% 8% 15% 7% 6% 5% 3 5% 5% 10%	7458

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	85% 7% 5% 2 1	3179
	11th to 20th	Day	65% 6% 13% 7% 7% 2	3570
	21st to end	Day	62% 8% 16% 13% 1	4004
February	1st to 10th	Day	75% 8% 7% 6% 3 1	1666
	11th to 20th	Day	71% 9% 10% 6% 4	1774
	21st to end	Day	74% 7% 7% 7% 4 1	1650
March	1st to 10th	Day	51% 9% 16% 15% 10%	4518
	11th to 20th	Day	55% 8% 21% 13% 2	4973
	21st to end	Day	69% 9% 12% 9% 3	5522
April	1st to 10th	Day	63% 9% 14% 13% 1	2422
	11th to 20th	Day	61% 11% 13% 13% 3	2570
	21st to end	Day	58% 11% 12% 15% 3 1	2537
May	1st to 10th	Day	59% 9% 11% 18% 3	4110
	11th to 20th	Day	45% 15% 20% 16% 4	4553
	21st to end	Day	58% 17% 14% 9% 2	5162
June	1st to 10th	Day	57% 10% 14% 15% 4	2850
	11th to 20th	Day	58% 9% 12% 14% 6% 1	2850
	21st to end	Day	35% 11% 17% 24% 12% 1	2850
July	1st to 10th	Day	22% 6% 11% 30% 22% 8%	4666
	11th to 20th	Day	13% 5% 7% 16% 32% 27%	4638
	21st to end	Day	13% 4 7% 23% 35% 17%	4639
August	1st to 10th	Day	23% 6% 13% 30% 22% 7%	4299
	11th to 20th	Day	23% 6% 16% 37% 17% 2	4067
	21st to end	Day	26% 6% 13% 36% 17% 2	4520
September	1st to 10th	Day	31% 8% 12% 26% 18% 6%	2295
	11th to 20th	Day	39% 9% 13% 23% 14% 2	2090
	21st to end	Day	41% 9% 18% 21% 10% 1	2090
October	1st to 10th	Day	31% 7% 20% 32% 10%	3376
	11th to 20th	Day	41% 8% 22% 22% 7%	2978
	21st to end	Day	59% 7% 17% 14% 2	3101
November	1st to 10th	Day	71% 8% 10% 7% 3 1	1734
	11th to 20th	Day	68% 10% 12% 6% 4 1	1600
	21st to end	Day	70% 12% 9% 6% 3	1445
December	1st to 10th	Day	58% 11% 20% 10% 1	2290
	11th to 20th	Day	71% 7% 17% 4 1	2644
	21st to end	Day	72% 7% 13% 6% 1	3498
January	1st to 10th	Night	83% 6% 5% 4 1	6766
	11th to 20th	Night	62% 7% 11% 7% 8% 4	6434
	21st to end	Night	62% 8% 19% 11% 1	6952
February	1st to 10th	Night	72% 8% 7% 8% 5% 1	2732
	11th to 20th	Night	71% 7% 9% 8% 4	2519
	21st to end	Night	71% 7% 7% 11% 3 1	1980
March	1st to 10th	Night	50% 8% 16% 13% 11%	5376
	11th to 20th	Night	50% 7% 20% 21% 3	5027
	21st to end	Night	68% 10% 11% 10% 1	5451
April	1st to 10th	Night	55% 10% 17% 15% 2	1977
	11th to 20th	Night	56% 9% 13% 16% 5%	1781
	21st to end	Night	51% 11% 14% 19% 5% 1	1759
May	1st to 10th	Night	55% 11% 12% 17% 5%	2860
	11th to 20th	Night	44% 12% 14% 24% 7%	2325
	21st to end	Night	58% 16% 15% 9% 3	2414
June	1st to 10th	Night	48% 11% 18% 18% 6%	1330
	11th to 20th	Night	52% 12% 12% 17% 6% 1	1330
	21st to end	Night	30% 8% 20% 26% 15% 1	1330
July	1st to 10th	Night	21% 5% 14% 27% 25% 8%	2185
	11th to 20th	Night	12% 3 8% 18% 28% 31%	2196
	21st to end	Night	13% 3 9% 24% 29% 22%	2674
August	1st to 10th	Night	18% 5% 14% 32% 23% 9%	2607
	11th to 20th	Night	23% 6% 18% 36% 15% 3	2838
	21st to end	Night	21% 5% 13% 36% 21% 3	3146
September	1st to 10th	Night	25% 9% 15% 27% 17% 7%	1882
	11th to 20th	Night	32% 10% 14% 28% 14% 2	2090
	21st to end	Night	35% 10% 19% 22% 12% 2	2090
October	1st to 10th	Night	32% 7% 18% 31% 11%	3599
	11th to 20th	Night	33% 8% 24% 26% 10%	3948
	21st to end	Night	48% 6% 23% 18% 5%	4457
November	1st to 10th	Night	66% 9% 12% 9% 4 1	2544
	11th to 20th	Night	67% 10% 12% 7% 4	2800
	21st to end	Night	69% 9% 11% 8% 3	2951
December	1st to 10th	Night	55% 11% 20% 12% 2	4890
	11th to 20th	Night	73% 9% 13% 4 1	5547
	21st to end	Night	71% 9% 13% 5% 2	7458

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% 15% 28% 17% 11% 2	200
	11th to 20th	Day	35% 17% 26% 14% 10%	200
	21st to end	Day	23% 20% 37% 14% 6%	220
February	1st to 10th	Day	29% 22% 35% 11% 3	234
	11th to 20th	Day	24% 23% 25% 22% 6%	310
	21st to end	Day	32% 23% 30% 13% 3	414
March	1st to 10th	Day	32% 22% 24% 15% 5% 1	500
	11th to 20th	Day	25% 21% 27% 17% 9% 2	500
	21st to end	Day	31% 22% 28% 13% 5% 1	550
April	1st to 10th	Day	27% 23% 31% 16% 3 1	500
	11th to 20th	Day	30% 23% 27% 15% 5%	492
	21st to end	Day	23% 22% 30% 17% 6% 2	481
May	1st to 10th	Day	20% 18% 27% 25% 8% 2	463
	11th to 20th	Day	23% 15% 25% 24% 13% 2	600
	21st to end	Day	28% 13% 20% 22% 14% 2	734
June	1st to 10th	Day	23% 16% 25% 24% 10% 2	680
	11th to 20th	Day	28% 20% 23% 19% 8% 1	680
	21st to end	Day	15% 14% 28% 28% 14% 2	680
July	1st to 10th	Day	9% 11% 29% 34% 15% 2	671
	11th to 20th	Day	9% 15% 32% 30% 12% 2	660
	21st to end	Day	5% 20% 34% 30% 10% 1	531
August	1st to 10th	Day	10% 15% 37% 28% 10% 1	487
	11th to 20th	Day	8% 14% 35% 27% 13% 3	477
	21st to end	Day	12% 19% 35% 25% 9% 2	539
September	1st to 10th	Day	15% 20% 30% 22% 10% 3	490
	11th to 20th	Day	18% 23% 28% 21% 8% 1	490
	21st to end	Day	23% 23% 28% 17% 7% 1	490
October	1st to 10th	Day	21% 17% 32% 21% 9% 1	428
	11th to 20th	Day	27% 17% 24% 18% 10% 4	300
	21st to end	Day	33% 21% 21% 19% 5% 1	330
November	1st to 10th	Day	35% 18% 28% 16% 3	300
	11th to 20th	Day	32% 16% 31% 15% 6%	300
	21st to end	Day	30% 19% 29% 12% 10%	223
December	1st to 10th	Day	35% 19% 23% 11% 12% 1	200
	11th to 20th	Day	32% 14% 34% 19% 2 1	200
	21st to end	Day	23% 20% 31% 19% 6% 1	220
January	1st to 10th	Night	35% 15% 27% 19% 4 1	1000
	11th to 20th	Night	32% 12% 30% 20% 5% 1	849
	21st to end	Night	28% 11% 36% 21% 4	880
February	1st to 10th	Night	31% 13% 34% 19% 4	800
	11th to 20th	Night	29% 13% 34% 20% 4	784
	21st to end	Night	23% 17% 31% 23% 5%	660
March	1st to 10th	Night	27% 15% 32% 20% 5% 1	800
	11th to 20th	Night	28% 12% 26% 27% 7% 1	800
	21st to end	Night	30% 12% 28% 22% 7%	880
April	1st to 10th	Night	23% 15% 29% 25% 8%	777
	11th to 20th	Night	25% 14% 30% 24% 6%	593
	21st to end	Night	23% 13% 25% 29% 9% 1	587
May	1st to 10th	Night	22% 10% 22% 34% 10% 1	570
	11th to 20th	Night	17% 7% 22% 36% 16% 2	389
	21st to end	Night	25% 11% 21% 23% 19% 1	411
June	1st to 10th	Night	24% 8% 22% 29% 14% 2	380
	11th to 20th	Night	27% 10% 24% 28% 11%	380
	21st to end	Night	11% 4 27% 39% 18% 1	380
July	1st to 10th	Night	7% 4 18% 53% 18% 1	370
	11th to 20th	Night	8% 5% 23% 51% 13%	368
	21st to end	Night	4 6% 20% 52% 17%	416
August	1st to 10th	Night	6% 6% 20% 48% 20%	425
	11th to 20th	Night	6% 6% 24% 41% 21% 2	564
	21st to end	Night	9% 8% 24% 41% 17% 1	627
September	1st to 10th	Night	9% 9% 27% 35% 18% 4	708
	11th to 20th	Night	13% 8% 24% 34% 19% 3	760
	21st to end	Night	20% 7% 23% 35% 14% 2	760
October	1st to 10th	Night	21% 8% 28% 33% 10% 1	760
	11th to 20th	Night	23% 8% 27% 31% 11% 1	760
	21st to end	Night	31% 11% 27% 25% 6%	836
November	1st to 10th	Night	36% 11% 28% 22% 3	789
	11th to 20th	Night	35% 16% 28% 18% 3	1000
	21st to end	Night	32% 14% 28% 22% 5%	1000
December	1st to 10th	Night	31% 12% 31% 20% 6%	1000
	11th to 20th	Night	32% 13% 33% 20% 2	1000
	21st to end	Night	34% 15% 30% 17% 3	1100

Page generated at 2025-04-23 07:25:07. Version ac07

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