Highvale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Highvale 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	9% 9% 3 8% 6% 5% 5% 4 6% 8% 35%	143222
	Night	9% 11% 4 10% 6% 5% 5% 4 6% 7% 32%	137828
Transparency	Day	45% 6% 17% 23% 8% 1	142917
	Night	49% 6% 15% 21% 9% 1	137716
Seeing	Day	13% 7% 24% 30% 19% 7%	18107
	Night	14% 6% 27% 35% 16% 2	26485

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% 14% 5% 11% 8% 5% 5% 3 5% 7% 29%	4125
	11th to 20th	Day	4 7% 3 8% 7% 6% 5% 5% 7% 9% 39%	4119
	21st to end	Day	6% 12% 4 10% 6% 5% 5% 4 6% 7% 35%	5006
February	1st to 10th	Day	8% 13% 5% 12% 6% 8% 6% 4 7% 7% 23%	1680
	11th to 20th	Day	5% 14% 6% 11% 7% 4 6% 5% 6% 7% 30%	1749
	21st to end	Day	4 15% 5% 12% 7% 8% 7% 5% 6% 7% 25%	1657
March	1st to 10th	Day	4 10% 4 11% 7% 6% 6% 4 6% 9% 32%	4618
	11th to 20th	Day	6% 12% 4 9% 6% 5% 4 4 6% 8% 36%	4990
	21st to end	Day	10% 15% 5% 13% 6% 5% 5% 4 5% 7% 23%	5782
April	1st to 10th	Day	7% 13% 4 9% 6% 5% 6% 6% 8% 7% 29%	2588
	11th to 20th	Day	11% 10% 4 8% 6% 5% 5% 5% 7% 7% 31%	2700
	21st to end	Day	10% 9% 4 9% 6% 6% 6% 4 6% 8% 32%	2743
May	1st to 10th	Day	9% 7% 3 7% 5% 5% 6% 4 6% 8% 39%	8547
	11th to 20th	Day	11% 10% 4 10% 7% 6% 6% 5% 7% 9% 26%	8755
	21st to end	Day	11% 6% 2 7% 6% 5% 6% 5% 7% 9% 34%	9649
June	1st to 10th	Day	15% 8% 3 7% 5% 5% 5% 4 7% 8% 33%	3150
	11th to 20th	Day	18% 8% 3 9% 7% 7% 6% 4 7% 7% 24%	3352
	21st to end	Day	11% 6% 2 6% 5% 5% 6% 5% 8% 9% 38%	3360
July	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 7% 9% 48%	7177
	11th to 20th	Day	10% 5% 2 7% 5% 5% 5% 4 6% 8% 42%	6780
	21st to end	Day	11% 6% 2 6% 4 5% 4 4 6% 9% 42%	7376
August	1st to 10th	Day	13% 5% 2 6% 4 5% 5% 4 7% 9% 40%	4578
	11th to 20th	Day	10% 6% 2 5% 5% 5% 4 4 7% 10% 41%	4345
	21st to end	Day	11% 5% 2 7% 5% 5% 5% 5% 7% 9% 40%	4664
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 3 6% 8% 43%	2505
	11th to 20th	Day	14% 7% 2 5% 3 4 4 3 5% 8% 44%	2221
	21st to end	Day	9% 8% 3 8% 5% 4 5% 4 6% 8% 40%	2200
October	1st to 10th	Day	9% 9% 4 8% 5% 4 5% 3 5% 7% 41%	3425
	11th to 20th	Day	11% 11% 4 7% 4 4 6% 4 6% 8% 34%	2932
	21st to end	Day	7% 12% 3 10% 6% 6% 5% 4 5% 7% 36%	3200
November	1st to 10th	Day	11% 17% 4 10% 7% 5% 4 5% 5% 6% 26%	1662
	11th to 20th	Day	7% 13% 5% 11% 5% 5% 4 2 7% 6% 34%	1470
	21st to end	Day	7% 11% 6% 13% 6% 7% 6% 5% 6% 7% 27%	1470
December	1st to 10th	Day	10% 15% 6% 13% 6% 6% 6% 4 6% 7% 21%	2360
	11th to 20th	Day	9% 13% 5% 14% 9% 5% 5% 3 6% 7% 24%	2712
	21st to end	Day	4 8% 3 10% 5% 5% 5% 4 6% 8% 41%	3575
January	1st to 10th	Night	8% 14% 5% 15% 8% 6% 5% 4 5% 6% 24%	8768
	11th to 20th	Night	3 8% 4 11% 7% 6% 6% 5% 6% 6% 38%	8779
	21st to end	Night	7% 13% 4 10% 6% 5% 5% 4 6% 7% 33%	9220
February	1st to 10th	Night	6% 14% 5% 12% 8% 7% 6% 3 5% 6% 27%	2940
	11th to 20th	Night	6% 12% 6% 11% 8% 6% 6% 5% 6% 6% 28%	2757
	21st to end	Night	5% 15% 5% 11% 8% 6% 6% 4 6% 7% 29%	2144
March	1st to 10th	Night	4 10% 4 12% 7% 7% 5% 4 7% 10% 31%	5496
	11th to 20th	Night	6% 12% 4 11% 7% 6% 7% 5% 7% 8% 28%	5229
	21st to end	Night	11% 16% 7% 13% 6% 5% 4 3 5% 6% 24%	5431
April	1st to 10th	Night	9% 10% 4 12% 7% 6% 6% 5% 6% 7% 28%	2032
	11th to 20th	Night	9% 12% 4 10% 7% 6% 6% 5% 8% 6% 27%	1871
	21st to end	Night	10% 11% 4 9% 4 4 5% 4 7% 9% 34%	1874
May	1st to 10th	Night	14% 8% 3 8% 5% 4 6% 4 5% 8% 36%	4371
	11th to 20th	Night	12% 9% 4 11% 7% 7% 6% 5% 7% 8% 24%	4105
	21st to end	Night	12% 7% 3 7% 5% 5% 6% 5% 6% 9% 36%	4522
June	1st to 10th	Night	18% 10% 3 9% 5% 5% 5% 4 6% 7% 28%	1470
	11th to 20th	Night	17% 8% 4 9% 8% 7% 6% 5% 8% 7% 20%	1263
	21st to end	Night	12% 7% 3 8% 4 6% 6% 5% 8% 9% 32%	1260
July	1st to 10th	Night	9% 5% 3 6% 5% 4 5% 4 7% 9% 43%	2782
	11th to 20th	Night	14% 6% 2 7% 6% 6% 6% 4 7% 9% 33%	3180
	21st to end	Night	14% 6% 2 6% 5% 4 4 4 6% 8% 41%	3467
August	1st to 10th	Night	15% 7% 2 6% 5% 5% 6% 4 6% 8% 37%	2569
	11th to 20th	Night	13% 8% 3 7% 5% 5% 4 4 6% 9% 37%	2705
	21st to end	Night	13% 5% 2 6% 4 4 5% 3 7% 8% 42%	3245
September	1st to 10th	Night	11% 5% 3 6% 4 5% 5% 4 6% 7% 45%	1891
	11th to 20th	Night	11% 7% 2 6% 4 4 5% 3 6% 8% 44%	2178
	21st to end	Night	10% 8% 3 7% 4 4 5% 4 6% 8% 42%	2200
October	1st to 10th	Night	9% 8% 3 8% 5% 5% 5% 4 6% 6% 39%	3767
	11th to 20th	Night	10% 8% 3 8% 5% 5% 5% 5% 6% 8% 36%	4216
	21st to end	Night	7% 10% 4 9% 6% 6% 5% 4 7% 8% 34%	4600
November	1st to 10th	Night	14% 15% 5% 10% 6% 5% 5% 3 5% 6% 27%	2833
	11th to 20th	Night	7% 14% 5% 11% 6% 6% 5% 4 6% 7% 28%	3150
	21st to end	Night	7% 13% 5% 11% 8% 6% 4 4 6% 8% 28%	3150
December	1st to 10th	Night	10% 18% 5% 10% 6% 5% 5% 4 5% 6% 25%	5040
	11th to 20th	Night	9% 16% 6% 13% 6% 6% 5% 4 6% 7% 22%	5700
	21st to end	Night	3 9% 4 10% 6% 6% 5% 4 5% 7% 41%	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	55% 4 12% 16% 13% 1	4125
	11th to 20th	Day	41% 5% 16% 17% 19% 2	4140
	21st to end	Day	47% 5% 20% 23% 5%	5007
February	1st to 10th	Day	58% 5% 13% 13% 9% 1	1680
	11th to 20th	Day	52% 8% 13% 17% 10%	1757
	21st to end	Day	55% 7% 12% 17% 7% 1	1657
March	1st to 10th	Day	48% 5% 17% 19% 11%	4618
	11th to 20th	Day	45% 6% 13% 24% 12%	4991
	21st to end	Day	58% 5% 10% 18% 8% 1	5782
April	1st to 10th	Day	49% 9% 15% 19% 7% 1	2588
	11th to 20th	Day	48% 6% 15% 21% 9% 1	2700
	21st to end	Day	47% 7% 15% 22% 8% 1	2743
May	1st to 10th	Day	42% 5% 10% 28% 14% 1	8547
	11th to 20th	Day	51% 6% 12% 24% 6%	8759
	21st to end	Day	43% 6% 22% 23% 6% 1	9650
June	1st to 10th	Day	47% 7% 17% 21% 8% 1	3150
	11th to 20th	Day	56% 8% 15% 15% 5%	3352
	21st to end	Day	39% 9% 21% 24% 6% 1	3360
July	1st to 10th	Day	32% 5% 20% 31% 12% 1	7099
	11th to 20th	Day	40% 5% 17% 30% 9%	6699
	21st to end	Day	38% 5% 23% 23% 10% 1	7169
August	1st to 10th	Day	39% 7% 20% 33% 2	4560
	11th to 20th	Day	36% 7% 22% 29% 6%	4387
	21st to end	Day	39% 5% 26% 24% 5%	4663
September	1st to 10th	Day	38% 7% 20% 27% 6% 2	2505
	11th to 20th	Day	38% 6% 20% 28% 8%	2221
	21st to end	Day	40% 8% 17% 25% 9% 2	2200
October	1st to 10th	Day	43% 4 23% 24% 5%	3425
	11th to 20th	Day	47% 5% 14% 25% 10%	2932
	21st to end	Day	47% 4 18% 26% 5%	3200
November	1st to 10th	Day	56% 6% 15% 16% 5% 1	1662
	11th to 20th	Day	49% 7% 17% 18% 9%	1470
	21st to end	Day	55% 7% 14% 16% 7% 1	1470
December	1st to 10th	Day	62% 5% 17% 11% 5% 1	2360
	11th to 20th	Day	59% 5% 16% 14% 5%	2714
	21st to end	Day	39% 5% 13% 27% 14% 2	3575
January	1st to 10th	Night	60% 4 11% 13% 10% 1	8769
	11th to 20th	Night	44% 4 15% 18% 15% 2	8820
	21st to end	Night	49% 4 21% 19% 7%	9220
February	1st to 10th	Night	56% 5% 12% 17% 9% 1	2940
	11th to 20th	Night	53% 7% 12% 16% 11% 1	2759
	21st to end	Night	53% 5% 10% 21% 10% 1	2144
March	1st to 10th	Night	47% 6% 17% 21% 9%	5496
	11th to 20th	Night	50% 6% 14% 19% 10%	5229
	21st to end	Night	59% 6% 9% 18% 7%	5431
April	1st to 10th	Night	52% 8% 13% 17% 9% 1	2032
	11th to 20th	Night	52% 7% 12% 18% 10% 2	1871
	21st to end	Night	45% 7% 13% 23% 11% 1	1874
May	1st to 10th	Night	45% 4 9% 25% 14% 2	4368
	11th to 20th	Night	55% 7% 12% 19% 7%	4105
	21st to end	Night	44% 6% 21% 22% 7% 1	4526
June	1st to 10th	Night	52% 8% 13% 18% 8% 1	1470
	11th to 20th	Night	57% 10% 16% 14% 3	1263
	21st to end	Night	44% 11% 18% 22% 4 1	1260
July	1st to 10th	Night	37% 6% 20% 22% 14%	2751
	11th to 20th	Night	46% 7% 14% 26% 6%	3138
	21st to end	Night	41% 6% 22% 24% 6% 1	3369
August	1st to 10th	Night	45% 7% 19% 28% 2	2562
	11th to 20th	Night	43% 7% 20% 21% 8%	2729
	21st to end	Night	38% 5% 23% 27% 6%	3245
September	1st to 10th	Night	35% 8% 19% 26% 11% 2	1891
	11th to 20th	Night	38% 6% 15% 28% 11% 2	2178
	21st to end	Night	39% 7% 15% 25% 13% 2	2200
October	1st to 10th	Night	45% 4 19% 25% 7%	3767
	11th to 20th	Night	44% 5% 13% 30% 8%	4216
	21st to end	Night	46% 6% 19% 23% 6%	4600
November	1st to 10th	Night	57% 5% 11% 19% 7%	2833
	11th to 20th	Night	53% 7% 13% 18% 7% 1	3150
	21st to end	Night	53% 6% 15% 18% 6% 2	3150
December	1st to 10th	Night	60% 6% 14% 15% 5% 1	5040
	11th to 20th	Night	61% 5% 16% 14% 5%	5697
	21st to end	Night	42% 4 13% 26% 13% 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	10% 6% 27% 31% 19% 7%	220
	11th to 20th	Day	11% 7% 30% 34% 14% 5%	220
	21st to end	Day	10% 11% 25% 33% 16% 5%	242
February	1st to 10th	Day	13% 10% 26% 38% 10% 3	220
	11th to 20th	Day	13% 5% 34% 31% 14% 3	278
	21st to end	Day	8% 9% 32% 31% 14% 5%	373
March	1st to 10th	Day	13% 8% 29% 30% 16% 4	540
	11th to 20th	Day	10% 5% 34% 30% 15% 6%	540
	21st to end	Day	16% 7% 26% 31% 16% 4	594
April	1st to 10th	Day	11% 12% 30% 29% 14% 4	540
	11th to 20th	Day	14% 8% 25% 29% 17% 6%	532
	21st to end	Day	14% 9% 26% 29% 16% 6%	540
May	1st to 10th	Day	14% 11% 22% 30% 18% 5%	663
	11th to 20th	Day	10% 8% 20% 35% 20% 6%	775
	21st to end	Day	16% 5% 21% 29% 21% 7%	844
June	1st to 10th	Day	17% 8% 24% 30% 16% 4	780
	11th to 20th	Day	20% 5% 20% 27% 21% 6%	982
	21st to end	Day	14% 3 20% 29% 26% 9%	990
July	1st to 10th	Day	11% 4 19% 35% 24% 8%	893
	11th to 20th	Day	13% 4 19% 31% 24% 9%	718
	21st to end	Day	11% 6% 17% 26% 28% 12%	794
August	1st to 10th	Day	10% 5% 17% 27% 26% 16%	551
	11th to 20th	Day	9% 5% 24% 29% 25% 7%	517
	21st to end	Day	14% 6% 15% 29% 25% 11%	583
September	1st to 10th	Day	14% 5% 26% 25% 22% 8%	530
	11th to 20th	Day	16% 5% 20% 32% 19% 8%	530
	21st to end	Day	12% 11% 30% 28% 14% 5%	530
October	1st to 10th	Day	14% 6% 25% 33% 16% 6%	445
	11th to 20th	Day	13% 10% 27% 30% 15% 5%	330
	21st to end	Day	13% 13% 34% 28% 10% 3	363
November	1st to 10th	Day	21% 6% 30% 29% 12% 2	328
	11th to 20th	Day	13% 5% 35% 33% 13% 2	220
	21st to end	Day	7% 7% 30% 37% 12% 6%	220
December	1st to 10th	Day	11% 5% 30% 37% 13% 4	220
	11th to 20th	Day	12% 10% 33% 29% 14% 3	220
	21st to end	Day	10% 4 24% 35% 21% 7%	242
January	1st to 10th	Night	13% 5% 32% 34% 15% 1	1050
	11th to 20th	Night	12% 10% 30% 34% 12% 1	1050
	21st to end	Night	14% 12% 31% 31% 11% 1	1007
February	1st to 10th	Night	10% 10% 25% 35% 17% 3	840
	11th to 20th	Night	10% 7% 31% 37% 14% 1	824
	21st to end	Night	10% 6% 27% 35% 17% 4	692
March	1st to 10th	Night	10% 5% 32% 34% 17% 2	840
	11th to 20th	Night	12% 4 30% 38% 14% 2	840
	21st to end	Night	16% 5% 25% 38% 14% 3	924
April	1st to 10th	Night	12% 7% 27% 37% 15% 1	772
	11th to 20th	Night	14% 5% 32% 34% 14% 1	623
	21st to end	Night	15% 7% 26% 37% 14% 1	614
May	1st to 10th	Night	14% 6% 26% 39% 12% 2	420
	11th to 20th	Night	14% 5% 26% 36% 19%	414
	21st to end	Night	20% 5% 19% 38% 16% 2	455
June	1st to 10th	Night	21% 9% 22% 33% 14% 1	420
	11th to 20th	Night	20% 4 19% 36% 19% 2	420
	21st to end	Night	14% 3 18% 36% 26% 3	420
July	1st to 10th	Night	15% 3 14% 46% 21% 1	390
	11th to 20th	Night	15% 2 19% 39% 24% 2	388
	21st to end	Night	13% 3 16% 37% 29% 2	438
August	1st to 10th	Night	13% 3 17% 32% 30% 5%	398
	11th to 20th	Night	14% 3 17% 36% 28% 3	472
	21st to end	Night	14% 3 19% 39% 24% 1	660
September	1st to 10th	Night	14% 2 19% 39% 24% 2	691
	11th to 20th	Night	15% 3 19% 40% 22% 1	800
	21st to end	Night	14% 5% 30% 35% 15% 2	800
October	1st to 10th	Night	16% 5% 26% 37% 15% 1	800
	11th to 20th	Night	14% 7% 31% 32% 15% 1	800
	21st to end	Night	14% 7% 31% 33% 13% 1	880
November	1st to 10th	Night	20% 6% 29% 33% 10% 1	988
	11th to 20th	Night	12% 8% 36% 32% 10% 2	1050
	21st to end	Night	14% 5% 35% 33% 12% 2	1050
December	1st to 10th	Night	16% 8% 32% 31% 11% 2	1050
	11th to 20th	Night	13% 7% 33% 32% 13% 2	1050
	21st to end	Night	13% 4 30% 34% 17% 2	1155

Page generated at 2026-06-28 00:10:43. Version ac07

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