Sunrise Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sunrise Point clear sky chart from 2005-11-06 to 2024-01-15.

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	8% 15% 6% 9% 6% 3 5% 4 5% 6% 33%	75005
	Night	7% 14% 6% 10% 8% 4 5% 5% 5% 6% 30%	74789
Transparency	Day	50% 9% 11% 16% 11% 2	74708
	Night	52% 10% 11% 14% 10% 3	74604
Seeing	Day	18% 23% 29% 20% 9% 2	13567
	Night	14% 19% 27% 25% 13% 2	22424

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% 21% 10% 13% 10% 4 5% 3 4 6% 16%	1519
	11th to 20th	Day	8% 18% 10% 12% 7% 3 4 5% 5% 6% 22%	1475
	21st to end	Day	6% 20% 8% 13% 7% 5% 4 5% 6% 5% 23%	1620
February	1st to 10th	Day	7% 18% 10% 13% 8% 4 7% 6% 5% 6% 17%	1620
	11th to 20th	Day	6% 18% 10% 13% 9% 4 6% 5% 4 5% 21%	1575
	21st to end	Day	6% 19% 12% 17% 9% 4 5% 5% 3 5% 16%	1430
March	1st to 10th	Day	4 19% 13% 15% 8% 4 6% 6% 4 5% 17%	1811
	11th to 20th	Day	8% 27% 10% 11% 7% 3 5% 4 5% 4 16%	1980
	21st to end	Day	8% 27% 13% 13% 8% 4 5% 4 3 4 10%	2272
April	1st to 10th	Day	9% 23% 11% 13% 7% 4 5% 4 5% 5% 14%	2160
	11th to 20th	Day	7% 25% 9% 11% 8% 3 5% 4 3 4 21%	2132
	21st to end	Day	7% 24% 7% 10% 7% 4 4 4 5% 6% 22%	2362
May	1st to 10th	Day	8% 21% 5% 7% 6% 4 5% 4 5% 6% 29%	2520
	11th to 20th	Day	12% 15% 4 9% 7% 4 7% 5% 6% 7% 23%	2477
	21st to end	Day	16% 18% 4 8% 7% 3 5% 5% 5% 5% 23%	2723
June	1st to 10th	Day	17% 14% 4 8% 5% 4 6% 5% 6% 6% 26%	2520
	11th to 20th	Day	13% 14% 5% 9% 7% 4 6% 6% 5% 7% 24%	2525
	21st to end	Day	9% 8% 3 6% 5% 3 4 5% 5% 7% 44%	2700
July	1st to 10th	Day	5% 5% 3 5% 5% 3 4 4 4 6% 57%	2561
	11th to 20th	Day	6% 4 2 4 3 2 4 3 4 6% 62%	2520
	21st to end	Day	4 3 1 2 3 2 2 2 3 5% 73%	2741
August	1st to 10th	Day	4 4 2 4 3 2 3 4 4 8% 62%	2482
	11th to 20th	Day	7% 3 1 3 3 2 3 3 5% 7% 63%	2298
	21st to end	Day	6% 5% 2 5% 5% 3 4 5% 5% 8% 52%	2428
September	1st to 10th	Day	7% 6% 2 4 4 3 4 4 5% 6% 56%	2160
	11th to 20th	Day	11% 9% 2 7% 6% 3 4 4 6% 6% 42%	2160
	21st to end	Day	10% 13% 4 6% 5% 3 4 4 5% 5% 42%	1917
October	1st to 10th	Day	14% 15% 3 7% 5% 3 4 5% 4 5% 36%	1800
	11th to 20th	Day	12% 16% 3 7% 6% 3 4 4 5% 6% 34%	1800
	21st to end	Day	12% 17% 5% 10% 6% 4 4 3 4 3 31%	1854
November	1st to 10th	Day	12% 24% 6% 11% 6% 4 6% 4 5% 5% 16%	1584
	11th to 20th	Day	10% 25% 7% 10% 7% 3 5% 5% 4 4 20%	1520
	21st to end	Day	7% 20% 8% 12% 8% 4 5% 3 3 5% 24%	1520
December	1st to 10th	Day	6% 17% 9% 14% 9% 4 5% 4 5% 5% 24%	1520
	11th to 20th	Day	6% 19% 8% 13% 9% 4 5% 5% 6% 5% 20%	1925
	21st to end	Day	4 19% 9% 12% 9% 5% 6% 6% 6% 5% 19%	2794
January	1st to 10th	Night	8% 18% 10% 14% 10% 4 6% 6% 4 4 16%	2646
	11th to 20th	Night	8% 17% 7% 11% 8% 4 5% 6% 5% 6% 22%	2590
	21st to end	Night	5% 16% 8% 13% 9% 4 6% 5% 5% 6% 23%	2732
February	1st to 10th	Night	6% 16% 8% 11% 11% 5% 6% 7% 5% 6% 18%	2340
	11th to 20th	Night	5% 15% 7% 13% 10% 4 6% 6% 5% 6% 25%	2272
	21st to end	Night	5% 14% 11% 15% 9% 5% 7% 6% 5% 5% 17%	1826
March	1st to 10th	Night	5% 14% 10% 13% 9% 5% 7% 7% 4 6% 20%	2147
	11th to 20th	Night	4 19% 8% 12% 8% 5% 7% 7% 5% 5% 19%	1979
	21st to end	Night	7% 19% 11% 15% 9% 5% 6% 5% 4 5% 14%	2084
April	1st to 10th	Night	5% 17% 10% 15% 10% 6% 6% 5% 4 6% 17%	1800
	11th to 20th	Night	6% 18% 8% 11% 7% 4 6% 6% 5% 5% 23%	1779
	21st to end	Night	7% 17% 6% 9% 9% 6% 6% 6% 6% 6% 20%	1596
May	1st to 10th	Night	6% 16% 7% 10% 8% 4 4 5% 5% 6% 30%	1440
	11th to 20th	Night	10% 9% 6% 8% 7% 6% 7% 6% 6% 7% 27%	1416
	21st to end	Night	10% 15% 7% 10% 8% 4 5% 5% 5% 7% 25%	1552
June	1st to 10th	Night	14% 14% 5% 8% 6% 5% 5% 5% 4 6% 28%	1440
	11th to 20th	Night	9% 15% 4 10% 7% 5% 5% 4 6% 8% 28%	1424
	21st to end	Night	7% 7% 3 6% 6% 3 5% 5% 6% 7% 46%	1260
July	1st to 10th	Night	3 4 3 4 6% 3 4 5% 4 7% 57%	1390
	11th to 20th	Night	5% 3 2 4 4 2 4 3 5% 6% 64%	1440
	21st to end	Night	3 3 1 2 3 2 2 3 3 5% 73%	1576
August	1st to 10th	Night	3 3 2 3 3 2 2 3 4 8% 68%	1455
	11th to 20th	Night	4 4 1 2 3 2 3 4 5% 6% 66%	1602
	21st to end	Night	4 5% 2 5% 4 3 4 4 5% 7% 56%	1927
September	1st to 10th	Night	6% 5% 1 4 4 3 5% 4 5% 7% 56%	1800
	11th to 20th	Night	8% 9% 4 8% 6% 4 4 5% 4 5% 45%	1800
	21st to end	Night	7% 10% 3 7% 6% 3 4 5% 6% 7% 42%	2041
October	1st to 10th	Night	11% 12% 3 8% 5% 3 4 4 4 6% 40%	2160
	11th to 20th	Night	9% 15% 5% 8% 7% 3 4 4 4 5% 35%	2160
	21st to end	Night	10% 16% 5% 8% 7% 3 4 4 5% 7% 32%	2501
November	1st to 10th	Night	11% 19% 6% 10% 8% 4 5% 5% 4 5% 21%	2492
	11th to 20th	Night	7% 17% 7% 12% 9% 4 6% 5% 5% 5% 22%	2660
	21st to end	Night	5% 17% 8% 13% 9% 4 5% 5% 5% 5% 23%	2660
December	1st to 10th	Night	5% 16% 7% 14% 8% 6% 6% 5% 4 5% 23%	2660
	11th to 20th	Night	7% 18% 8% 13% 10% 5% 6% 6% 5% 5% 17%	3280
	21st to end	Night	5% 17% 8% 15% 10% 6% 7% 6% 5% 4 17%	4862

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	70% 9% 6% 8% 5% 1	1519
	11th to 20th	Day	60% 9% 11% 9% 8% 4	1475
	21st to end	Day	61% 8% 9% 12% 8% 2	1620
February	1st to 10th	Day	64% 12% 10% 10% 5% 1	1620
	11th to 20th	Day	63% 10% 9% 10% 6% 2	1584
	21st to end	Day	68% 8% 8% 8% 5% 1	1430
March	1st to 10th	Day	65% 11% 9% 10% 5% 1	1811
	11th to 20th	Day	68% 8% 7% 12% 4	1980
	21st to end	Day	74% 10% 9% 6% 1	2272
April	1st to 10th	Day	68% 9% 11% 10% 2	2160
	11th to 20th	Day	63% 9% 10% 10% 7% 1	2132
	21st to end	Day	62% 9% 11% 11% 6% 1	2362
May	1st to 10th	Day	53% 10% 14% 16% 6%	2520
	11th to 20th	Day	54% 11% 14% 15% 5%	2480
	21st to end	Day	59% 11% 13% 14% 3	2724
June	1st to 10th	Day	54% 10% 15% 13% 7% 1	2520
	11th to 20th	Day	53% 12% 18% 11% 5% 1	2525
	21st to end	Day	34% 10% 18% 22% 13% 2	2700
July	1st to 10th	Day	28% 9% 12% 26% 19% 6%	2492
	11th to 20th	Day	24% 6% 10% 25% 28% 7%	2445
	21st to end	Day	14% 5% 10% 28% 35% 9%	2589
August	1st to 10th	Day	19% 8% 16% 27% 24% 6%	2465
	11th to 20th	Day	19% 6% 15% 32% 23% 4	2298
	21st to end	Day	28% 10% 13% 27% 20% 2	2428
September	1st to 10th	Day	26% 6% 12% 26% 24% 6%	2160
	11th to 20th	Day	40% 8% 11% 18% 18% 5%	2160
	21st to end	Day	42% 8% 13% 19% 14% 4	1917
October	1st to 10th	Day	48% 6% 10% 22% 13% 3	1800
	11th to 20th	Day	49% 7% 13% 17% 13% 1	1800
	21st to end	Day	57% 7% 7% 15% 13% 1	1854
November	1st to 10th	Day	66% 9% 9% 10% 4 2	1584
	11th to 20th	Day	67% 8% 8% 9% 6% 2	1520
	21st to end	Day	62% 7% 7% 10% 9% 4	1520
December	1st to 10th	Day	61% 10% 8% 10% 9% 2	1520
	11th to 20th	Day	63% 11% 9% 12% 5%	1928
	21st to end	Day	65% 9% 10% 9% 6% 1	2794
January	1st to 10th	Night	69% 10% 9% 6% 5% 2	2646
	11th to 20th	Night	59% 9% 11% 10% 6% 5%	2590
	21st to end	Night	59% 10% 7% 12% 9% 4	2732
February	1st to 10th	Night	63% 11% 10% 10% 6% 1	2340
	11th to 20th	Night	57% 12% 11% 11% 6% 3	2274
	21st to end	Night	66% 10% 9% 9% 5% 1	1826
March	1st to 10th	Night	59% 11% 10% 13% 5% 1	2147
	11th to 20th	Night	61% 13% 9% 12% 5% 1	1980
	21st to end	Night	66% 12% 11% 9% 1	2084
April	1st to 10th	Night	66% 12% 11% 9% 4	1800
	11th to 20th	Night	55% 12% 12% 12% 8% 1	1779
	21st to end	Night	57% 13% 11% 12% 7% 1	1596
May	1st to 10th	Night	51% 9% 14% 17% 7% 1	1440
	11th to 20th	Night	48% 12% 16% 17% 6% 1	1416
	21st to end	Night	51% 14% 15% 15% 4	1552
June	1st to 10th	Night	51% 10% 14% 16% 7% 1	1440
	11th to 20th	Night	48% 12% 18% 16% 5% 1	1424
	21st to end	Night	31% 10% 18% 25% 13% 2	1260
July	1st to 10th	Night	25% 11% 13% 24% 20% 7%	1350
	11th to 20th	Night	20% 7% 13% 26% 24% 10%	1392
	21st to end	Night	12% 6% 10% 24% 37% 11%	1488
August	1st to 10th	Night	15% 8% 14% 28% 27% 9%	1447
	11th to 20th	Night	18% 7% 15% 27% 28% 5%	1602
	21st to end	Night	26% 9% 12% 28% 22% 4	1927
September	1st to 10th	Night	24% 10% 14% 23% 23% 7%	1800
	11th to 20th	Night	38% 11% 8% 18% 18% 7%	1800
	21st to end	Night	37% 10% 14% 18% 15% 6%	2041
October	1st to 10th	Night	43% 7% 10% 23% 14% 2	2160
	11th to 20th	Night	49% 9% 10% 16% 14% 2	2160
	21st to end	Night	51% 9% 9% 15% 14% 2	2501
November	1st to 10th	Night	63% 9% 10% 12% 5% 1	2492
	11th to 20th	Night	64% 9% 8% 10% 7% 2	2660
	21st to end	Night	59% 10% 8% 8% 11% 4	2660
December	1st to 10th	Night	62% 9% 10% 9% 9% 2	2660
	11th to 20th	Night	66% 12% 9% 8% 5%	3276
	21st to end	Night	66% 12% 11% 6% 4	4862

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	24% 33% 22% 12% 7% 2	180
	11th to 20th	Day	19% 33% 23% 15% 10%	169
	21st to end	Day	18% 32% 22% 17% 10%	212
February	1st to 10th	Day	25% 35% 24% 12% 4	340
	11th to 20th	Day	27% 31% 26% 14% 2	335
	21st to end	Day	25% 26% 28% 16% 4	324
March	1st to 10th	Day	19% 34% 29% 16% 2	420
	11th to 20th	Day	25% 27% 26% 17% 5%	420
	21st to end	Day	27% 31% 26% 13% 3	462
April	1st to 10th	Day	28% 27% 27% 11% 5% 2	420
	11th to 20th	Day	25% 32% 25% 11% 6% 2	412
	21st to end	Day	25% 29% 26% 13% 7% 1	420
May	1st to 10th	Day	19% 24% 31% 21% 5% 1	423
	11th to 20th	Day	26% 16% 32% 15% 8% 3	448
	21st to end	Day	25% 19% 25% 21% 9% 2	485
June	1st to 10th	Day	21% 23% 25% 21% 9% 1	450
	11th to 20th	Day	21% 28% 31% 12% 7% 1	455
	21st to end	Day	11% 19% 34% 23% 11% 2	630
July	1st to 10th	Day	7% 16% 38% 32% 7% 1	487
	11th to 20th	Day	8% 14% 38% 27% 11% 2	444
	21st to end	Day	2 12% 31% 36% 16% 2	487
August	1st to 10th	Day	6% 12% 31% 30% 16% 5%	447
	11th to 20th	Day	5% 8% 30% 35% 17% 6%	437
	21st to end	Day	7% 18% 34% 26% 11% 4	495
September	1st to 10th	Day	10% 16% 36% 26% 9% 2	450
	11th to 20th	Day	14% 17% 32% 25% 11% 1	450
	21st to end	Day	17% 20% 28% 23% 10% 1	450
October	1st to 10th	Day	19% 21% 26% 20% 13% 2	450
	11th to 20th	Day	24% 20% 25% 16% 11% 3	450
	21st to end	Day	27% 23% 25% 14% 9% 2	369
November	1st to 10th	Day	24% 29% 27% 14% 5%	228
	11th to 20th	Day	28% 25% 19% 14% 11% 2	180
	21st to end	Day	23% 24% 24% 16% 12% 1	180
December	1st to 10th	Day	24% 25% 23% 13% 12% 3	180
	11th to 20th	Day	17% 37% 23% 18% 4 1	180
	21st to end	Day	20% 24% 32% 18% 6% 1	198
January	1st to 10th	Night	22% 29% 24% 16% 7% 1	760
	11th to 20th	Night	19% 25% 26% 20% 9% 2	740
	21st to end	Night	14% 24% 26% 26% 9% 2	792
February	1st to 10th	Night	17% 24% 32% 19% 7% 1	720
	11th to 20th	Night	17% 22% 26% 26% 8%	704
	21st to end	Night	20% 21% 31% 22% 5% 1	592
March	1st to 10th	Night	14% 24% 29% 22% 10% 1	720
	11th to 20th	Night	13% 27% 29% 22% 8% 1	720
	21st to end	Night	16% 26% 32% 18% 6% 2	792
April	1st to 10th	Night	16% 22% 30% 24% 7% 2	720
	11th to 20th	Night	15% 22% 31% 22% 8% 3	711
	21st to end	Night	13% 20% 33% 22% 11% 1	516
May	1st to 10th	Night	12% 20% 25% 28% 14% 2	360
	11th to 20th	Night	14% 13% 22% 30% 20% 2	354
	21st to end	Night	12% 13% 26% 29% 18% 2	389
June	1st to 10th	Night	16% 14% 25% 31% 13% 1	360
	11th to 20th	Night	11% 18% 32% 26% 13%	360
	21st to end	Night	9% 9% 24% 35% 22% 1	360
July	1st to 10th	Night	3 6% 25% 43% 22% 1	350
	11th to 20th	Night	4 5% 25% 44% 21% 1	348
	21st to end	Night	3 5% 19% 41% 31% 3	394
August	1st to 10th	Night	4 5% 17% 38% 32% 4	381
	11th to 20th	Night	4 3 16% 34% 33% 9%	534
	21st to end	Night	6% 9% 24% 35% 23% 3	739
September	1st to 10th	Night	8% 7% 25% 33% 23% 3	720
	11th to 20th	Night	10% 9% 21% 28% 25% 6%	720
	21st to end	Night	11% 14% 22% 31% 20% 2	720
October	1st to 10th	Night	15% 13% 24% 29% 18% 2	720
	11th to 20th	Night	17% 15% 26% 23% 16% 4	720
	21st to end	Night	20% 21% 24% 23% 9% 3	792
November	1st to 10th	Night	20% 21% 33% 20% 6%	740
	11th to 20th	Night	23% 25% 24% 20% 7% 1	760
	21st to end	Night	16% 26% 26% 21% 10% 1	760
December	1st to 10th	Night	17% 22% 28% 24% 8% 1	760
	11th to 20th	Night	18% 25% 34% 16% 7%	760
	21st to end	Night	19% 28% 33% 15% 5%	836

Page generated at 2024-01-12 13:17:42. Version ac07

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