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 2024-02-05.

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% 9% 4 7% 7% 4 5% 6% 6% 8% 34%	78145
	Night	9% 10% 5% 8% 7% 4 6% 5% 6% 7% 32%	80657
Transparency	Day	46% 8% 18% 21% 7% 1	77842
	Night	49% 7% 15% 20% 9% 1	80540
Seeing	Day	13% 6% 24% 30% 20% 7%	14792
	Night	14% 6% 27% 35% 16% 2	23480

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% 7% 12% 10% 3 5% 4 5% 7% 30%	2219
	11th to 20th	Day	7% 10% 4 9% 7% 3 5% 7% 7% 8% 34%	2199
	21st to end	Day	8% 12% 4 8% 8% 3 5% 5% 6% 7% 34%	2698
February	1st to 10th	Day	9% 12% 6% 11% 8% 5% 7% 6% 7% 7% 22%	1472
	11th to 20th	Day	6% 13% 7% 11% 8% 3 6% 6% 6% 7% 27%	1493
	21st to end	Day	5% 12% 7% 10% 8% 6% 7% 7% 6% 8% 24%	1417
March	1st to 10th	Day	7% 14% 6% 10% 10% 4 6% 5% 5% 7% 26%	1800
	11th to 20th	Day	8% 10% 4 7% 6% 3 5% 6% 7% 8% 34%	1928
	21st to end	Day	9% 13% 5% 8% 7% 4 6% 6% 7% 9% 25%	2246
April	1st to 10th	Day	8% 11% 5% 8% 7% 4 7% 7% 7% 8% 29%	2218
	11th to 20th	Day	12% 11% 5% 7% 7% 3 5% 6% 7% 7% 30%	2310
	21st to end	Day	11% 8% 4 7% 7% 3 7% 6% 6% 9% 32%	2350
May	1st to 10th	Day	13% 9% 3 8% 7% 4 7% 6% 6% 9% 28%	2622
	11th to 20th	Day	8% 7% 3 6% 6% 4 5% 5% 6% 8% 42%	2654
	21st to end	Day	18% 7% 3 6% 6% 3 5% 5% 6% 8% 33%	2917
June	1st to 10th	Day	16% 8% 3 6% 6% 4 6% 6% 7% 9% 32%	2700
	11th to 20th	Day	19% 8% 3 7% 8% 4 7% 5% 7% 8% 24%	2872
	21st to end	Day	10% 5% 2 5% 6% 4 6% 6% 8% 10% 38%	2880
July	1st to 10th	Day	11% 6% 3 7% 5% 4 5% 6% 7% 9% 38%	2858
	11th to 20th	Day	11% 6% 3 5% 6% 3 6% 7% 7% 10% 35%	2700
	21st to end	Day	9% 5% 2 4 6% 4 6% 6% 7% 8% 44%	2938
August	1st to 10th	Day	10% 5% 2 6% 7% 4 6% 6% 7% 10% 37%	2529
	11th to 20th	Day	8% 5% 2 4 5% 4 4 5% 7% 10% 43%	2406
	21st to end	Day	11% 6% 3 5% 5% 3 5% 6% 7% 9% 40%	2574
September	1st to 10th	Day	13% 7% 3 5% 5% 3 4 5% 5% 7% 42%	2255
	11th to 20th	Day	15% 7% 2 5% 4 3 4 5% 5% 8% 42%	1999
	21st to end	Day	10% 8% 3 7% 6% 3 5% 5% 5% 8% 40%	1980
October	1st to 10th	Day	11% 10% 4 8% 6% 4 4 4 4 6% 40%	1893
	11th to 20th	Day	11% 10% 4 6% 4 3 5% 6% 5% 8% 38%	1620
	21st to end	Day	9% 12% 3 9% 8% 5% 6% 5% 5% 6% 31%	1782
November	1st to 10th	Day	11% 17% 5% 9% 8% 4 4 5% 5% 6% 26%	1502
	11th to 20th	Day	7% 12% 6% 11% 7% 4 4 3 7% 6% 34%	1330
	21st to end	Day	7% 10% 6% 10% 8% 5% 6% 6% 6% 7% 29%	1330
December	1st to 10th	Day	6% 11% 7% 12% 8% 5% 7% 5% 5% 7% 27%	1330
	11th to 20th	Day	7% 12% 5% 10% 10% 4 6% 5% 5% 9% 28%	1682
	21st to end	Day	4 8% 4 8% 7% 3 6% 5% 7% 9% 39%	2442
January	1st to 10th	Night	4 13% 6% 11% 10% 5% 5% 5% 5% 6% 29%	4726
	11th to 20th	Night	5% 9% 5% 10% 10% 5% 6% 6% 7% 6% 31%	4699
	21st to end	Night	6% 14% 5% 9% 8% 4 6% 4 6% 7% 31%	4990
February	1st to 10th	Night	7% 13% 6% 11% 9% 5% 5% 5% 5% 7% 27%	2582
	11th to 20th	Night	6% 12% 7% 9% 9% 5% 7% 6% 6% 6% 27%	2353
	21st to end	Night	6% 13% 6% 9% 8% 4 6% 5% 6% 7% 30%	1834
March	1st to 10th	Night	6% 12% 5% 9% 10% 5% 5% 5% 7% 8% 28%	2160
	11th to 20th	Night	8% 10% 5% 8% 8% 4 7% 6% 6% 8% 30%	2031
	21st to end	Night	8% 15% 7% 9% 8% 5% 5% 5% 6% 7% 26%	2106
April	1st to 10th	Night	10% 9% 5% 10% 8% 5% 6% 6% 7% 7% 28%	1742
	11th to 20th	Night	10% 11% 4 9% 8% 4 6% 6% 7% 6% 28%	1601
	21st to end	Night	11% 11% 4 7% 5% 3 5% 5% 6% 10% 34%	1607
May	1st to 10th	Night	14% 9% 4 8% 8% 4 7% 6% 6% 7% 26%	1337
	11th to 20th	Night	10% 10% 4 6% 6% 3 6% 5% 7% 8% 36%	1239
	21st to end	Night	19% 9% 4 6% 5% 4 6% 4 5% 7% 31%	1358
June	1st to 10th	Night	18% 9% 3 8% 6% 4 6% 6% 6% 8% 28%	1260
	11th to 20th	Night	18% 8% 4 7% 8% 5% 7% 6% 8% 8% 21%	1083
	21st to end	Night	11% 5% 4 7% 6% 4 7% 7% 9% 9% 31%	1080
July	1st to 10th	Night	14% 5% 3 5% 5% 3 6% 6% 7% 9% 37%	1100
	11th to 20th	Night	10% 6% 3 7% 7% 4 7% 8% 7% 11% 31%	1260
	21st to end	Night	10% 5% 3 5% 5% 4 6% 5% 7% 9% 40%	1379
August	1st to 10th	Night	11% 6% 2 6% 6% 4 6% 5% 6% 8% 38%	1407
	11th to 20th	Night	10% 6% 2 5% 6% 4 4 6% 7% 9% 40%	1492
	21st to end	Night	12% 6% 3 6% 5% 3 5% 5% 8% 9% 39%	1782
September	1st to 10th	Night	12% 6% 3 5% 5% 4 5% 4 6% 7% 42%	1701
	11th to 20th	Night	13% 7% 3 5% 5% 3 5% 4 6% 8% 42%	1960
	21st to end	Night	11% 7% 3 6% 5% 3 4 5% 6% 7% 43%	1980
October	1st to 10th	Night	11% 9% 3 8% 6% 3 5% 5% 6% 6% 38%	2064
	11th to 20th	Night	9% 10% 4 7% 6% 3 4 5% 6% 8% 37%	2340
	21st to end	Night	9% 10% 4 9% 7% 4 6% 5% 7% 7% 32%	2574
November	1st to 10th	Night	14% 14% 6% 9% 7% 4 5% 4 5% 6% 26%	2556
	11th to 20th	Night	8% 14% 6% 10% 7% 4 5% 5% 5% 7% 28%	2850
	21st to end	Night	8% 11% 5% 10% 9% 5% 5% 5% 6% 8% 29%	2850
December	1st to 10th	Night	9% 14% 5% 8% 7% 5% 5% 6% 6% 7% 30%	2850
	11th to 20th	Night	8% 14% 6% 10% 7% 5% 5% 5% 6% 7% 28%	3510
	21st to end	Night	4 9% 4 8% 6% 4 6% 5% 5% 7% 42%	5214

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	53% 6% 15% 19% 7% 1	2219
	11th to 20th	Day	45% 7% 12% 13% 21% 2	2220
	21st to end	Day	47% 8% 20% 20% 5%	2698
February	1st to 10th	Day	58% 6% 14% 13% 7% 1	1472
	11th to 20th	Day	54% 9% 14% 16% 7%	1501
	21st to end	Day	54% 8% 13% 17% 8%	1417
March	1st to 10th	Day	56% 7% 15% 17% 5% 1	1800
	11th to 20th	Day	44% 8% 13% 23% 11% 1	1929
	21st to end	Day	53% 7% 17% 17% 5%	2246
April	1st to 10th	Day	49% 10% 15% 18% 7% 1	2218
	11th to 20th	Day	50% 7% 15% 21% 7% 1	2310
	21st to end	Day	46% 8% 16% 21% 7% 2	2350
May	1st to 10th	Day	51% 8% 14% 18% 9% 1	2622
	11th to 20th	Day	39% 6% 15% 29% 11%	2658
	21st to end	Day	47% 7% 15% 21% 9% 1	2918
June	1st to 10th	Day	47% 7% 18% 21% 6%	2700
	11th to 20th	Day	56% 9% 16% 14% 5%	2872
	21st to end	Day	38% 10% 23% 24% 5% 1	2880
July	1st to 10th	Day	41% 9% 20% 24% 5% 1	2780
	11th to 20th	Day	42% 10% 26% 19% 2	2619
	21st to end	Day	35% 10% 28% 25% 4	2775
August	1st to 10th	Day	39% 11% 27% 21% 3	2511
	11th to 20th	Day	33% 9% 27% 25% 6%	2406
	21st to end	Day	38% 8% 24% 23% 7%	2574
September	1st to 10th	Day	40% 8% 20% 25% 6% 1	2255
	11th to 20th	Day	39% 6% 20% 27% 7%	1999
	21st to end	Day	40% 8% 16% 25% 9% 2	1980
October	1st to 10th	Day	47% 5% 16% 23% 8% 1	1893
	11th to 20th	Day	43% 8% 16% 23% 9%	1620
	21st to end	Day	51% 7% 13% 22% 7% 1	1782
November	1st to 10th	Day	57% 7% 14% 16% 5% 1	1502
	11th to 20th	Day	50% 7% 16% 18% 9%	1330
	21st to end	Day	53% 7% 15% 17% 7% 1	1330
December	1st to 10th	Day	56% 7% 12% 16% 8% 2	1330
	11th to 20th	Day	53% 6% 16% 17% 7%	1684
	21st to end	Day	39% 7% 13% 23% 16% 3	2442
January	1st to 10th	Night	54% 6% 15% 16% 8% 2	4726
	11th to 20th	Night	49% 6% 12% 14% 16% 3	4740
	21st to end	Night	50% 7% 19% 16% 8% 1	4990
February	1st to 10th	Night	56% 5% 13% 17% 8% 1	2582
	11th to 20th	Night	55% 7% 13% 15% 9%	2355
	21st to end	Night	52% 5% 11% 20% 10% 1	1834
March	1st to 10th	Night	51% 8% 15% 20% 6% 1	2160
	11th to 20th	Night	50% 7% 11% 20% 11% 1	2031
	21st to end	Night	54% 8% 14% 17% 6% 1	2106
April	1st to 10th	Night	52% 9% 13% 17% 9% 1	1742
	11th to 20th	Night	53% 7% 11% 19% 9% 2	1601
	21st to end	Night	45% 8% 14% 22% 10% 1	1607
May	1st to 10th	Night	54% 8% 11% 18% 9% 1	1337
	11th to 20th	Night	43% 7% 12% 23% 14% 1	1239
	21st to end	Night	52% 6% 13% 17% 10% 2	1358
June	1st to 10th	Night	52% 9% 14% 18% 7%	1260
	11th to 20th	Night	56% 11% 17% 13% 2	1083
	21st to end	Night	43% 13% 19% 21% 4 1	1080
July	1st to 10th	Night	41% 11% 20% 21% 6% 1	1069
	11th to 20th	Night	44% 14% 22% 15% 5%	1218
	21st to end	Night	36% 11% 23% 26% 3	1302
August	1st to 10th	Night	41% 10% 22% 24% 3	1400
	11th to 20th	Night	38% 9% 23% 24% 6% 1	1492
	21st to end	Night	39% 8% 17% 26% 9% 1	1782
September	1st to 10th	Night	38% 8% 19% 24% 9% 2	1701
	11th to 20th	Night	40% 7% 15% 28% 9% 2	1960
	21st to end	Night	38% 8% 14% 25% 13% 1	1980
October	1st to 10th	Night	46% 7% 13% 25% 10%	2064
	11th to 20th	Night	44% 7% 14% 26% 9% 1	2340
	21st to end	Night	48% 8% 15% 21% 7% 1	2574
November	1st to 10th	Night	58% 6% 12% 18% 7%	2556
	11th to 20th	Night	54% 7% 13% 18% 7% 1	2850
	21st to end	Night	52% 7% 16% 18% 6% 2	2850
December	1st to 10th	Night	52% 6% 12% 19% 9% 2	2850
	11th to 20th	Night	54% 6% 16% 17% 6%	3507
	21st to end	Night	40% 6% 14% 24% 14% 2	5214

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% 6% 24% 33% 21% 8%	180
	11th to 20th	Day	12% 4 28% 34% 17% 5%	180
	21st to end	Day	11% 10% 23% 34% 17% 5%	198
February	1st to 10th	Day	15% 10% 28% 35% 9% 4	168
	11th to 20th	Day	14% 6% 36% 29% 12% 2	202
	21st to end	Day	8% 7% 30% 33% 17% 7%	283
March	1st to 10th	Day	13% 9% 28% 30% 17% 3	420
	11th to 20th	Day	10% 5% 33% 31% 15% 6%	420
	21st to end	Day	16% 6% 27% 29% 16% 5%	462
April	1st to 10th	Day	11% 12% 31% 30% 12% 4	420
	11th to 20th	Day	15% 6% 22% 32% 17% 8%	412
	21st to end	Day	14% 9% 26% 30% 15% 6%	420
May	1st to 10th	Day	14% 10% 22% 29% 20% 5%	525
	11th to 20th	Day	10% 6% 20% 37% 21% 6%	625
	21st to end	Day	19% 4 19% 29% 22% 8%	679
June	1st to 10th	Day	17% 5% 24% 32% 16% 5%	630
	11th to 20th	Day	21% 6% 18% 28% 22% 6%	802
	21st to end	Day	12% 3 20% 29% 27% 9%	810
July	1st to 10th	Day	12% 3 19% 33% 25% 8%	775
	11th to 20th	Day	13% 4 18% 32% 25% 8%	618
	21st to end	Day	10% 6% 17% 27% 28% 13%	684
August	1st to 10th	Day	10% 5% 17% 28% 25% 16%	469
	11th to 20th	Day	8% 5% 24% 29% 26% 7%	437
	21st to end	Day	15% 5% 16% 31% 24% 9%	495
September	1st to 10th	Day	16% 5% 28% 25% 20% 6%	450
	11th to 20th	Day	17% 5% 21% 32% 18% 7%	450
	21st to end	Day	12% 10% 28% 28% 15% 6%	450
October	1st to 10th	Day	16% 6% 24% 32% 16% 7%	374
	11th to 20th	Day	13% 12% 26% 29% 16% 5%	270
	21st to end	Day	13% 12% 34% 27% 11% 2	297
November	1st to 10th	Day	21% 7% 28% 31% 12% 2	269
	11th to 20th	Day	13% 5% 34% 32% 13% 2	180
	21st to end	Day	7% 9% 32% 36% 12% 6%	180
December	1st to 10th	Day	10% 6% 25% 40% 14% 5%	180
	11th to 20th	Day	13% 11% 30% 29% 13% 3	180
	21st to end	Day	8% 4 25% 34% 23% 8%	198
January	1st to 10th	Night	13% 5% 32% 34% 15% 1	950
	11th to 20th	Night	12% 9% 29% 35% 13% 2	950
	21st to end	Night	14% 12% 30% 31% 12% 1	912
February	1st to 10th	Night	10% 11% 25% 33% 18% 3	738
	11th to 20th	Night	11% 8% 32% 34% 14% 1	704
	21st to end	Night	10% 6% 24% 36% 19% 5%	592
March	1st to 10th	Night	11% 5% 31% 33% 18% 2	720
	11th to 20th	Night	12% 4 29% 39% 14% 2	720
	21st to end	Night	16% 4 25% 38% 14% 3	792
April	1st to 10th	Night	12% 7% 27% 37% 16% 2	662
	11th to 20th	Night	15% 5% 30% 33% 15% 1	533
	21st to end	Night	17% 6% 26% 36% 15% 1	527
May	1st to 10th	Night	14% 6% 23% 40% 14% 3	360
	11th to 20th	Night	14% 5% 25% 37% 19% 1	354
	21st to end	Night	22% 5% 19% 37% 16% 2	389
June	1st to 10th	Night	21% 7% 21% 35% 15% 2	360
	11th to 20th	Night	20% 4 18% 37% 19% 2	360
	21st to end	Night	12% 3 20% 36% 26% 4	360
July	1st to 10th	Night	16% 3 14% 46% 21% 1	350
	11th to 20th	Night	15% 2 20% 40% 22% 2	348
	21st to end	Night	11% 4 16% 39% 28% 3	394
August	1st to 10th	Night	13% 3 16% 33% 30% 5%	358
	11th to 20th	Night	14% 2 17% 38% 27% 3	424
	21st to end	Night	14% 3 19% 39% 24% 1	594
September	1st to 10th	Night	15% 2 20% 39% 22% 2	621
	11th to 20th	Night	16% 4 20% 39% 20% 1	720
	21st to end	Night	15% 4 27% 36% 16% 2	720
October	1st to 10th	Night	17% 4 25% 37% 16% 1	720
	11th to 20th	Night	14% 7% 30% 33% 16% 1	720
	21st to end	Night	14% 6% 31% 34% 13% 1	792
November	1st to 10th	Night	20% 6% 29% 33% 11% 2	891
	11th to 20th	Night	12% 8% 36% 31% 10% 2	950
	21st to end	Night	13% 5% 36% 33% 11% 2	950
December	1st to 10th	Night	15% 9% 30% 32% 12% 2	950
	11th to 20th	Night	12% 6% 33% 33% 14% 2	950
	21st to end	Night	12% 4 30% 33% 17% 2	1045

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