Highland Meadows Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Highland Meadows Observing Site clear sky chart from 2005-11-06 to 2026-02-01.

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	7% 10% 3 9% 6% 5% 5% 4 6% 7% 38%	131400
	Night	6% 11% 4 9% 6% 5% 5% 4 6% 7% 38%	129358
Transparency	Day	43% 9% 14% 20% 11% 3	131114
	Night	45% 10% 15% 18% 9% 3	129221
Seeing	Day	14% 15% 25% 26% 16% 4	16723
	Night	13% 9% 22% 36% 18% 2	26056

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	5% 21% 10% 23% 11% 7% 5% 3 4 3 7%	3269
	11th to 20th	Day	7% 12% 5% 14% 9% 8% 8% 5% 5% 5% 22%	3696
	21st to end	Day	8% 17% 6% 16% 6% 5% 4 4 6% 5% 22%	4092
February	1st to 10th	Day	8% 17% 6% 16% 8% 6% 5% 5% 5% 6% 17%	1641
	11th to 20th	Day	5% 16% 7% 14% 8% 8% 6% 5% 6% 7% 20%	1795
	21st to end	Day	5% 17% 7% 14% 8% 7% 6% 5% 5% 6% 20%	1650
March	1st to 10th	Day	4 12% 4 8% 6% 5% 6% 6% 6% 10% 33%	4518
	11th to 20th	Day	5% 14% 4 10% 7% 6% 6% 4 6% 6% 32%	4927
	21st to end	Day	7% 17% 5% 13% 7% 7% 6% 5% 7% 7% 18%	5587
April	1st to 10th	Day	6% 15% 5% 11% 7% 7% 6% 5% 7% 8% 23%	2400
	11th to 20th	Day	9% 13% 4 11% 8% 6% 6% 5% 6% 6% 26%	2570
	21st to end	Day	10% 13% 4 10% 6% 6% 6% 5% 6% 6% 28%	2600
May	1st to 10th	Day	10% 11% 4 9% 4 5% 4 3 4 6% 41%	5914
	11th to 20th	Day	9% 8% 3 10% 7% 7% 8% 5% 8% 9% 26%	6474
	21st to end	Day	9% 8% 3 7% 5% 5% 6% 5% 7% 8% 38%	7405
June	1st to 10th	Day	16% 9% 2 8% 6% 5% 6% 4 6% 7% 31%	3000
	11th to 20th	Day	15% 9% 3 7% 7% 6% 5% 5% 7% 8% 28%	3000
	21st to end	Day	6% 5% 2 6% 5% 5% 5% 5% 7% 9% 46%	3000
July	1st to 10th	Day	4 3 1 3 3 5% 5% 3 5% 6% 61%	6780
	11th to 20th	Day	4 2 1 2 2 2 2 2 4 5% 74%	6649
	21st to end	Day	3 2 1 3 2 2 3 3 5% 8% 68%	6874
August	1st to 10th	Day	5% 3 1 3 3 4 5% 4 7% 8% 57%	4489
	11th to 20th	Day	5% 3 1 4 4 4 4 3 6% 8% 58%	4158
	21st to end	Day	5% 4 1 5% 3 3 4 3 5% 7% 59%	4664
September	1st to 10th	Day	5% 3 1 5% 3 4 3 4 6% 7% 57%	2403
	11th to 20th	Day	7% 6% 2 6% 4 4 5% 4 6% 9% 46%	2200
	21st to end	Day	7% 5% 2 6% 4 6% 6% 4 6% 8% 46%	2200
October	1st to 10th	Day	6% 5% 2 5% 4 4 4 3 5% 6% 57%	3534
	11th to 20th	Day	7% 7% 2 7% 4 4 5% 4 7% 9% 43%	3033
	21st to end	Day	9% 13% 4 11% 7% 7% 6% 5% 6% 7% 26%	3200
November	1st to 10th	Day	11% 19% 5% 11% 7% 7% 5% 5% 5% 8% 17%	1854
	11th to 20th	Day	8% 16% 6% 13% 7% 7% 6% 4 6% 8% 20%	1686
	21st to end	Day	7% 18% 5% 12% 8% 7% 6% 4 6% 6% 19%	1491
December	1st to 10th	Day	4 11% 5% 11% 8% 7% 11% 7% 7% 6% 23%	2360
	11th to 20th	Day	7% 16% 6% 16% 9% 9% 7% 4 5% 5% 15%	2712
	21st to end	Day	6% 19% 7% 22% 12% 8% 6% 3 4 4 10%	3575
January	1st to 10th	Night	7% 23% 8% 19% 10% 6% 5% 4 4 4 11%	6916
	11th to 20th	Night	5% 10% 5% 13% 8% 7% 7% 4 4 5% 31%	6445
	21st to end	Night	9% 18% 6% 10% 6% 5% 5% 6% 6% 5% 24%	7106
February	1st to 10th	Night	9% 17% 4 12% 7% 6% 6% 3 6% 5% 24%	2757
	11th to 20th	Night	6% 15% 6% 12% 8% 6% 5% 4 5% 5% 27%	2489
	21st to end	Night	4 15% 5% 12% 7% 6% 6% 5% 6% 7% 26%	1980
March	1st to 10th	Night	2 9% 4 8% 5% 5% 6% 5% 8% 9% 38%	5376
	11th to 20th	Night	3 9% 4 9% 7% 6% 5% 4 6% 6% 40%	5072
	21st to end	Night	6% 15% 5% 12% 7% 8% 6% 5% 7% 8% 21%	5385
April	1st to 10th	Night	6% 11% 3 7% 6% 6% 5% 4 7% 8% 37%	2000
	11th to 20th	Night	6% 11% 4 7% 6% 5% 5% 5% 5% 7% 37%	1781
	21st to end	Night	7% 10% 2 8% 5% 5% 6% 5% 5% 7% 39%	1800
May	1st to 10th	Night	9% 9% 3 8% 6% 4 4 4 6% 8% 40%	4062
	11th to 20th	Night	9% 8% 3 7% 6% 5% 6% 5% 8% 9% 36%	3416
	21st to end	Night	11% 8% 2 6% 4 4 4 4 4 7% 45%	3470
June	1st to 10th	Night	11% 7% 3 6% 4 5% 5% 4 6% 7% 42%	1400
	11th to 20th	Night	11% 6% 2 7% 6% 6% 6% 6% 6% 8% 37%	1400
	21st to end	Night	5% 4 2 6% 4 3 4 4 6% 8% 56%	1400
July	1st to 10th	Night	4 1 2 2 3 3 2 4 6% 71%	3180
	11th to 20th	Night	4 2 1 3 1 2 2 2 2 5% 76%	3308
	21st to end	Night	3 2 1 3 4 3 3 2 4 6% 70%	3969
August	1st to 10th	Night	3 3 1 3 3 3 3 3 4 7% 68%	2662
	11th to 20th	Night	3 2 1 5% 4 5% 5% 4 7% 8% 56%	2901
	21st to end	Night	3 3 1 3 3 2 4 3 6% 8% 64%	3245
September	1st to 10th	Night	4 3 2 5% 3 3 4 3 5% 7% 61%	1994
	11th to 20th	Night	5% 4 2 5% 3 5% 4 4 6% 8% 53%	2200
	21st to end	Night	6% 5% 2 5% 3 5% 4 4 6% 9% 53%	2200
October	1st to 10th	Night	4 4 2 5% 4 3 5% 4 6% 8% 56%	3664
	11th to 20th	Night	4 5% 2 5% 4 4 5% 4 6% 9% 52%	4113
	21st to end	Night	5% 7% 2 7% 5% 5% 5% 4 7% 9% 43%	4600
November	1st to 10th	Night	11% 14% 5% 9% 6% 6% 6% 5% 6% 8% 26%	2665
	11th to 20th	Night	8% 16% 5% 11% 7% 6% 5% 4 6% 6% 27%	2911
	21st to end	Night	8% 17% 6% 11% 7% 6% 5% 4 6% 6% 24%	3128
December	1st to 10th	Night	4 12% 4 8% 6% 5% 7% 6% 5% 7% 35%	5040
	11th to 20th	Night	5% 16% 7% 18% 9% 7% 6% 4 5% 6% 16%	5700
	21st to end	Night	7% 17% 7% 18% 9% 7% 5% 4 5% 6% 16%	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% 8% 6% 3 1	3269
	11th to 20th	Day	62% 9% 14% 10% 4 1	3720
	21st to end	Day	62% 11% 13% 12% 2	4092
February	1st to 10th	Day	66% 10% 12% 7% 3 1	1641
	11th to 20th	Day	60% 14% 13% 8% 4	1804
	21st to end	Day	65% 9% 11% 9% 4 1	1650
March	1st to 10th	Day	41% 10% 19% 18% 11%	4518
	11th to 20th	Day	48% 10% 22% 16% 4	4928
	21st to end	Day	60% 13% 13% 11% 3	5587
April	1st to 10th	Day	57% 11% 15% 14% 2	2400
	11th to 20th	Day	55% 10% 14% 16% 4	2570
	21st to end	Day	53% 10% 14% 15% 6% 1	2600
May	1st to 10th	Day	42% 6% 12% 25% 14% 1	5914
	11th to 20th	Day	44% 13% 19% 18% 7%	6478
	21st to end	Day	38% 12% 19% 23% 8% 1	7406
June	1st to 10th	Day	50% 9% 14% 19% 7%	3000
	11th to 20th	Day	50% 11% 13% 16% 8% 2	3000
	21st to end	Day	32% 11% 17% 26% 14% 1	3000
July	1st to 10th	Day	22% 6% 11% 26% 24% 10%	6706
	11th to 20th	Day	14% 3 9% 27% 23% 23%	6568
	21st to end	Day	16% 4 8% 32% 27% 14%	6681
August	1st to 10th	Day	22% 7% 12% 30% 24% 5%	4472
	11th to 20th	Day	22% 8% 14% 38% 18% 2	4197
	21st to end	Day	24% 6% 14% 33% 20% 3	4663
September	1st to 10th	Day	25% 7% 13% 31% 18% 5%	2403
	11th to 20th	Day	33% 10% 16% 25% 15% 2	2200
	21st to end	Day	35% 9% 21% 24% 10% 1	2200
October	1st to 10th	Day	28% 5% 20% 36% 10%	3534
	11th to 20th	Day	36% 8% 23% 25% 7%	3033
	21st to end	Day	54% 9% 19% 16% 3	3200
November	1st to 10th	Day	65% 11% 13% 8% 3	1854
	11th to 20th	Day	63% 12% 14% 7% 4	1686
	21st to end	Day	64% 13% 12% 7% 3	1491
December	1st to 10th	Day	57% 18% 17% 8% 1	2360
	11th to 20th	Day	68% 10% 17% 5% 1	2714
	21st to end	Day	72% 12% 10% 5% 1	3575
January	1st to 10th	Night	76% 10% 6% 7% 1	6916
	11th to 20th	Night	55% 10% 13% 11% 8% 3	6483
	21st to end	Night	58% 13% 14% 12% 2	7106
February	1st to 10th	Night	62% 10% 12% 10% 5% 1	2757
	11th to 20th	Night	59% 13% 14% 10% 5%	2490
	21st to end	Night	57% 11% 14% 13% 4 1	1980
March	1st to 10th	Night	37% 12% 22% 17% 13%	5376
	11th to 20th	Night	41% 11% 21% 22% 5%	5072
	21st to end	Night	56% 15% 15% 11% 2	5385
April	1st to 10th	Night	43% 14% 20% 20% 4	2000
	11th to 20th	Night	45% 10% 17% 19% 7% 1	1781
	21st to end	Night	43% 11% 17% 20% 7% 1	1800
May	1st to 10th	Night	40% 9% 14% 22% 15%	4059
	11th to 20th	Night	39% 11% 17% 24% 9%	3416
	21st to end	Night	37% 9% 16% 26% 11% 1	3470
June	1st to 10th	Night	40% 10% 20% 21% 9% 1	1400
	11th to 20th	Night	43% 11% 14% 21% 9% 2	1400
	21st to end	Night	25% 9% 17% 29% 18% 2	1400
July	1st to 10th	Night	15% 6% 11% 28% 26% 14%	3145
	11th to 20th	Night	14% 2 8% 28% 20% 28%	3266
	21st to end	Night	16% 5% 10% 30% 22% 18%	3857
August	1st to 10th	Night	16% 5% 13% 32% 24% 10%	2654
	11th to 20th	Night	22% 7% 13% 36% 18% 4	2928
	21st to end	Night	17% 5% 13% 36% 24% 4	3245
September	1st to 10th	Night	22% 7% 15% 31% 18% 7%	1994
	11th to 20th	Night	27% 7% 16% 31% 16% 3	2200
	21st to end	Night	28% 10% 21% 24% 15% 2	2200
October	1st to 10th	Night	27% 6% 20% 35% 12%	3664
	11th to 20th	Night	29% 10% 21% 28% 12%	4113
	21st to end	Night	38% 9% 25% 22% 7%	4600
November	1st to 10th	Night	58% 11% 15% 11% 4	2665
	11th to 20th	Night	58% 13% 16% 9% 4	2911
	21st to end	Night	61% 12% 14% 10% 3	3128
December	1st to 10th	Night	47% 16% 20% 15% 2	5040
	11th to 20th	Night	69% 11% 14% 6% 1	5697
	21st to end	Night	68% 12% 13% 6% 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	17% 15% 20% 31% 12% 5%	220
	11th to 20th	Day	17% 10% 28% 30% 10% 5%	220
	21st to end	Day	15% 13% 27% 31% 12% 2	242
February	1st to 10th	Day	18% 19% 30% 24% 8%	221
	11th to 20th	Day	13% 16% 25% 31% 13% 1	340
	21st to end	Day	19% 19% 29% 24% 7% 1	414
March	1st to 10th	Day	16% 21% 31% 19% 11% 2	500
	11th to 20th	Day	17% 16% 24% 25% 14% 4	500
	21st to end	Day	19% 20% 29% 20% 9% 3	550
April	1st to 10th	Day	17% 22% 32% 19% 8% 2	500
	11th to 20th	Day	18% 25% 29% 16% 10% 2	492
	21st to end	Day	18% 22% 25% 21% 11% 3	500
May	1st to 10th	Day	17% 16% 24% 30% 11% 3	503
	11th to 20th	Day	20% 12% 25% 24% 15% 5%	608
	21st to end	Day	20% 11% 18% 27% 20% 5%	789
June	1st to 10th	Day	16% 14% 26% 22% 18% 3	730
	11th to 20th	Day	17% 18% 27% 22% 14% 2	730
	21st to end	Day	10% 12% 25% 25% 22% 6%	730
July	1st to 10th	Day	5% 8% 24% 31% 27% 6%	721
	11th to 20th	Day	5% 11% 23% 33% 24% 4	665
	21st to end	Day	3 11% 26% 30% 25% 5%	575
August	1st to 10th	Day	8% 10% 25% 30% 21% 6%	527
	11th to 20th	Day	6% 9% 25% 28% 22% 10%	517
	21st to end	Day	9% 12% 22% 32% 18% 7%	583
September	1st to 10th	Day	8% 13% 24% 28% 19% 7%	530
	11th to 20th	Day	9% 12% 27% 26% 19% 7%	530
	21st to end	Day	12% 18% 26% 25% 16% 4	530
October	1st to 10th	Day	14% 12% 25% 29% 14% 5%	490
	11th to 20th	Day	17% 14% 22% 27% 13% 7%	330
	21st to end	Day	23% 13% 25% 24% 12% 2	363
November	1st to 10th	Day	21% 18% 25% 25% 11%	330
	11th to 20th	Day	17% 18% 26% 27% 11% 2	330
	21st to end	Day	16% 15% 28% 26% 13% 2	231
December	1st to 10th	Day	21% 15% 20% 22% 14% 7%	220
	11th to 20th	Day	18% 18% 25% 25% 14% 2	220
	21st to end	Day	13% 13% 25% 33% 14% 2	242
January	1st to 10th	Night	21% 13% 24% 31% 9% 1	1050
	11th to 20th	Night	18% 9% 25% 34% 12% 2	850
	21st to end	Night	16% 10% 23% 40% 10% 1	924
February	1st to 10th	Night	17% 12% 26% 32% 11% 2	800
	11th to 20th	Night	15% 10% 26% 37% 11% 1	784
	21st to end	Night	16% 12% 23% 32% 16% 2	660
March	1st to 10th	Night	10% 12% 26% 36% 14% 2	800
	11th to 20th	Night	13% 12% 24% 34% 16% 2	800
	21st to end	Night	14% 11% 25% 31% 16% 2	880
April	1st to 10th	Night	12% 9% 25% 35% 17% 2	800
	11th to 20th	Night	11% 12% 29% 34% 13% 1	593
	21st to end	Night	12% 12% 26% 33% 17% 1	600
May	1st to 10th	Night	11% 9% 24% 37% 17% 2	588
	11th to 20th	Night	10% 6% 19% 34% 28% 3	394
	21st to end	Night	17% 5% 18% 30% 26% 4	433
June	1st to 10th	Night	13% 7% 20% 36% 22% 3	400
	11th to 20th	Night	14% 7% 29% 31% 19% 2	400
	21st to end	Night	7% 3 16% 39% 31% 4	400
July	1st to 10th	Night	3 2 12% 46% 35% 2	390
	11th to 20th	Night	4 4 13% 49% 30% 1	388
	21st to end	Night	3 2 12% 45% 35% 3	438
August	1st to 10th	Night	3 2 13% 41% 37% 4	425
	11th to 20th	Night	3 3 14% 40% 34% 5%	594
	21st to end	Night	6% 4 16% 44% 27% 3	660
September	1st to 10th	Night	7% 1 15% 41% 30% 6%	779
	11th to 20th	Night	7% 5% 14% 36% 34% 5%	800
	21st to end	Night	9% 6% 18% 38% 24% 4	800
October	1st to 10th	Night	10% 8% 18% 39% 23% 3	800
	11th to 20th	Night	11% 9% 19% 38% 21% 3	800
	21st to end	Night	15% 11% 24% 36% 13% 1	880
November	1st to 10th	Night	18% 12% 22% 38% 10% 1	820
	11th to 20th	Night	19% 15% 25% 29% 11%	1021
	21st to end	Night	15% 12% 24% 35% 13% 1	1050
December	1st to 10th	Night	16% 12% 21% 35% 13% 3	1050
	11th to 20th	Night	19% 10% 26% 36% 10%	1050
	21st to end	Night	19% 11% 26% 31% 12%	1155

Page generated at 2026-01-28 23:21:41. Version ac07

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