Craven
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Craven clear sky chart from 2005-11-06 to 2026-10-29.

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% 8% 3 8% 5% 5% 5% 4 6% 8% 39%	153996
	Night	7% 9% 4 9% 6% 5% 5% 4 6% 8% 37%	146907
Transparency	Day	42% 6% 16% 25% 11% 1	153709
	Night	45% 6% 15% 23% 10% 1	146779
Seeing	Day	12% 9% 30% 29% 16% 4	18724
	Night	12% 7% 31% 36% 13% 1	28045

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	6% 13% 4 13% 9% 10% 7% 5% 7% 6% 19%	4102
	11th to 20th	Day	3 7% 4 10% 11% 9% 10% 8% 10% 8% 20%	4514
	21st to end	Day	5% 11% 6% 11% 8% 6% 6% 4 6% 9% 30%	5188
February	1st to 10th	Day	7% 12% 6% 13% 9% 7% 8% 6% 6% 6% 20%	1727
	11th to 20th	Day	8% 12% 5% 10% 6% 7% 8% 6% 8% 7% 26%	1845
	21st to end	Day	5% 11% 5% 14% 9% 8% 7% 5% 8% 6% 22%	1683
March	1st to 10th	Day	6% 12% 5% 15% 7% 5% 6% 4 5% 8% 28%	4600
	11th to 20th	Day	6% 13% 6% 15% 6% 5% 4 4 6% 7% 28%	4870
	21st to end	Day	9% 12% 5% 14% 5% 4 5% 4 5% 6% 30%	6026
April	1st to 10th	Day	7% 9% 4 8% 6% 5% 6% 5% 6% 8% 38%	2520
	11th to 20th	Day	13% 13% 4 10% 6% 5% 4 4 6% 7% 29%	2522
	21st to end	Day	13% 11% 4 8% 4 5% 4 4 5% 6% 36%	2914
May	1st to 10th	Day	12% 7% 2 5% 4 4 4 4 5% 7% 45%	8224
	11th to 20th	Day	16% 8% 2 6% 5% 5% 5% 5% 7% 9% 33%	8191
	21st to end	Day	10% 5% 2 7% 4 5% 5% 4 5% 7% 46%	9267
June	1st to 10th	Day	15% 5% 2 7% 5% 4 5% 5% 6% 7% 38%	3297
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	3360
	21st to end	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 9% 40%	3360
July	1st to 10th	Day	5% 5% 2 6% 4 4 5% 5% 7% 9% 48%	9186
	11th to 20th	Day	9% 6% 2 7% 4 5% 5% 5% 8% 9% 40%	8636
	21st to end	Day	4 3 1 4 3 3 4 3 6% 8% 60%	8952
August	1st to 10th	Day	7% 6% 2 6% 4 5% 5% 4 5% 7% 49%	6462
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 7% 9% 46%	6390
	21st to end	Day	11% 5% 2 5% 3 3 3 3 5% 7% 52%	6216
September	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 5% 8% 47%	2520
	11th to 20th	Day	13% 7% 2 7% 4 3 4 4 6% 7% 42%	2510
	21st to end	Day	11% 5% 2 5% 3 3 4 3 5% 8% 51%	2273
October	1st to 10th	Day	9% 8% 3 6% 4 4 5% 4 6% 8% 42%	3370
	11th to 20th	Day	7% 8% 3 5% 3 4 4 4 6% 10% 46%	3200
	21st to end	Day	8% 10% 5% 8% 5% 4 4 4 6% 7% 40%	3262
November	1st to 10th	Day	13% 15% 5% 9% 5% 5% 5% 3 5% 6% 29%	1715
	11th to 20th	Day	6% 13% 5% 14% 9% 6% 5% 4 5% 7% 26%	1680
	21st to end	Day	9% 11% 6% 13% 6% 6% 6% 5% 5% 6% 26%	1497
December	1st to 10th	Day	6% 14% 5% 15% 8% 9% 7% 4 5% 7% 23%	2360
	11th to 20th	Day	7% 15% 7% 13% 9% 8% 6% 4 5% 6% 19%	2499
	21st to end	Day	4 8% 4 14% 7% 5% 6% 5% 5% 5% 37%	3058
January	1st to 10th	Night	4 11% 5% 15% 10% 8% 7% 5% 6% 7% 21%	8786
	11th to 20th	Night	3 9% 4 12% 9% 10% 8% 6% 8% 7% 23%	8401
	21st to end	Night	5% 10% 5% 12% 7% 6% 5% 4 6% 8% 31%	9026
February	1st to 10th	Night	7% 11% 5% 13% 8% 7% 6% 6% 7% 6% 24%	2911
	11th to 20th	Night	5% 10% 4 14% 6% 6% 7% 5% 6% 7% 29%	2662
	21st to end	Night	3 7% 4 12% 10% 7% 6% 5% 7% 9% 32%	2123
March	1st to 10th	Night	6% 11% 5% 13% 6% 6% 6% 5% 7% 7% 27%	5494
	11th to 20th	Night	7% 11% 3 11% 9% 6% 5% 4 7% 8% 29%	5335
	21st to end	Night	7% 13% 5% 14% 7% 6% 6% 4 5% 7% 27%	5171
April	1st to 10th	Night	6% 9% 4 7% 5% 5% 4 4 7% 7% 42%	2100
	11th to 20th	Night	13% 12% 3 8% 5% 4 5% 4 6% 7% 32%	2048
	21st to end	Night	12% 9% 4 8% 5% 5% 5% 4 7% 7% 35%	1704
May	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 5% 7% 48%	4724
	11th to 20th	Night	18% 8% 2 6% 5% 5% 5% 4 6% 8% 33%	4702
	21st to end	Night	10% 6% 2 6% 4 3 5% 3 6% 8% 47%	4920
June	1st to 10th	Night	11% 6% 3 5% 4 3 4 4 5% 9% 44%	1319
	11th to 20th	Night	15% 7% 2 6% 3 4 5% 5% 6% 8% 38%	1260
	21st to end	Night	10% 5% 2 6% 5% 3 4 4 7% 10% 43%	1260
July	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 7% 10% 48%	3770
	11th to 20th	Night	9% 4 2 6% 4 4 5% 4 6% 9% 47%	4320
	21st to end	Night	5% 3 1 4 3 3 3 3 5% 7% 61%	5150
August	1st to 10th	Night	4 3 1 4 3 4 4 4 7% 10% 56%	3708
	11th to 20th	Night	6% 3 1 5% 4 4 4 4 7% 11% 51%	3676
	21st to end	Night	8% 4 2 6% 4 4 4 3 5% 8% 51%	4929
September	1st to 10th	Night	9% 4 1 5% 3 5% 4 3 5% 8% 52%	2100
	11th to 20th	Night	10% 7% 2 6% 4 4 5% 3 6% 8% 46%	2110
	21st to end	Night	10% 5% 1 5% 4 3 4 4 5% 6% 52%	2344
October	1st to 10th	Night	11% 7% 2 5% 3 4 4 3 6% 8% 46%	4040
	11th to 20th	Night	6% 7% 2 6% 3 4 4 4 6% 9% 50%	4135
	21st to end	Night	9% 9% 3 7% 4 3 4 4 6% 7% 44%	4715
November	1st to 10th	Night	15% 14% 4 8% 6% 4 4 3 4 5% 32%	2800
	11th to 20th	Night	8% 14% 5% 12% 7% 5% 5% 4 5% 6% 29%	2940
	21st to end	Night	8% 12% 5% 12% 6% 6% 4 4 6% 8% 30%	3120
December	1st to 10th	Night	7% 16% 7% 15% 9% 7% 6% 4 5% 6% 19%	5050
	11th to 20th	Night	7% 14% 6% 12% 9% 8% 8% 5% 6% 6% 19%	5914
	21st to end	Night	4 7% 4 12% 7% 6% 5% 4 5% 6% 39%	8140

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	63% 6% 12% 11% 8%	4102
	11th to 20th	Day	55% 6% 15% 16% 7%	4538
	21st to end	Day	51% 5% 20% 17% 7%	5188
February	1st to 10th	Day	61% 6% 12% 15% 6%	1727
	11th to 20th	Day	55% 6% 12% 15% 11%	1854
	21st to end	Day	58% 6% 13% 15% 8%	1683
March	1st to 10th	Day	54% 5% 19% 16% 5%	4600
	11th to 20th	Day	54% 8% 17% 17% 4	4871
	21st to end	Day	53% 6% 13% 18% 9% 1	6026
April	1st to 10th	Day	41% 7% 17% 23% 11% 1	2520
	11th to 20th	Day	53% 6% 14% 19% 6% 2	2522
	21st to end	Day	47% 6% 14% 23% 8% 1	2914
May	1st to 10th	Day	38% 4 10% 31% 16% 2	8224
	11th to 20th	Day	45% 6% 14% 22% 13% 1	8195
	21st to end	Day	35% 6% 12% 27% 19% 1	9267
June	1st to 10th	Day	42% 8% 13% 26% 10% 1	3297
	11th to 20th	Day	51% 7% 13% 19% 9% 1	3360
	21st to end	Day	37% 10% 17% 27% 9%	3360
July	1st to 10th	Day	30% 6% 26% 30% 9%	9110
	11th to 20th	Day	38% 6% 15% 31% 9% 2	8555
	21st to end	Day	22% 4 17% 35% 20% 2	8759
August	1st to 10th	Day	34% 5% 18% 28% 14% 1	6446
	11th to 20th	Day	33% 5% 20% 36% 7%	6432
	21st to end	Day	33% 3 14% 34% 15% 1	6215
September	1st to 10th	Day	34% 6% 14% 29% 14% 2	2520
	11th to 20th	Day	41% 7% 14% 27% 10% 1	2510
	21st to end	Day	32% 5% 14% 33% 15% 2	2273
October	1st to 10th	Day	40% 4 16% 29% 10% 1	3370
	11th to 20th	Day	34% 4 16% 35% 10% 2	3200
	21st to end	Day	43% 4 18% 27% 8%	3262
November	1st to 10th	Day	56% 6% 15% 16% 7%	1715
	11th to 20th	Day	58% 7% 14% 15% 6%	1680
	21st to end	Day	56% 10% 15% 15% 4	1497
December	1st to 10th	Day	61% 7% 17% 11% 4	2360
	11th to 20th	Day	65% 6% 18% 8% 2	2499
	21st to end	Day	49% 4 11% 22% 10% 5%	3058
January	1st to 10th	Night	60% 6% 12% 16% 6%	8787
	11th to 20th	Night	56% 6% 15% 15% 8%	8439
	21st to end	Night	51% 6% 19% 17% 7%	9026
February	1st to 10th	Night	57% 7% 12% 17% 7%	2911
	11th to 20th	Night	50% 7% 13% 19% 10%	2663
	21st to end	Night	46% 6% 16% 23% 8%	2123
March	1st to 10th	Night	52% 6% 22% 15% 4	5494
	11th to 20th	Night	51% 6% 19% 19% 5%	5335
	21st to end	Night	55% 6% 11% 20% 8%	5171
April	1st to 10th	Night	38% 6% 15% 25% 16%	2100
	11th to 20th	Night	50% 5% 12% 21% 10% 3	2048
	21st to end	Night	46% 8% 10% 23% 12% 1	1704
May	1st to 10th	Night	36% 4 9% 33% 16% 2	4724
	11th to 20th	Night	47% 6% 13% 22% 11% 1	4702
	21st to end	Night	32% 7% 11% 28% 20% 2	4924
June	1st to 10th	Night	36% 4 16% 28% 14% 2	1319
	11th to 20th	Night	42% 7% 16% 22% 12% 1	1260
	21st to end	Night	34% 8% 18% 30% 8% 1	1260
July	1st to 10th	Night	31% 6% 25% 32% 6% 1	3737
	11th to 20th	Night	33% 5% 14% 37% 10% 2	4278
	21st to end	Night	23% 4 17% 33% 20% 3	5038
August	1st to 10th	Night	24% 5% 23% 33% 14% 1	3700
	11th to 20th	Night	26% 5% 23% 37% 8% 1	3700
	21st to end	Night	32% 4 14% 31% 18% 1	4929
September	1st to 10th	Night	30% 6% 12% 30% 19% 2	2100
	11th to 20th	Night	35% 7% 15% 27% 14% 1	2110
	21st to end	Night	32% 5% 13% 31% 17% 2	2344
October	1st to 10th	Night	36% 4 18% 30% 10% 2	4040
	11th to 20th	Night	31% 4 14% 37% 13% 1	4135
	21st to end	Night	39% 4 13% 34% 9% 1	4715
November	1st to 10th	Night	54% 6% 13% 18% 7% 1	2800
	11th to 20th	Night	55% 6% 17% 15% 6%	2940
	21st to end	Night	53% 7% 17% 19% 4	3120
December	1st to 10th	Night	66% 7% 14% 9% 3	5050
	11th to 20th	Night	65% 5% 17% 10% 3	5913
	21st to end	Night	45% 4 11% 23% 12% 4	8140

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	12% 8% 32% 30% 15% 3	220
	11th to 20th	Day	10% 12% 31% 31% 14% 2	293
	21st to end	Day	12% 11% 32% 31% 12% 2	363
February	1st to 10th	Day	11% 10% 38% 30% 10% 2	330
	11th to 20th	Day	10% 6% 33% 32% 15% 4	330
	21st to end	Day	6% 7% 33% 35% 17% 2	273
March	1st to 10th	Day	13% 10% 34% 29% 12% 2	330
	11th to 20th	Day	10% 12% 37% 26% 12% 3	431
	21st to end	Day	13% 11% 34% 26% 13% 2	594
April	1st to 10th	Day	9% 15% 38% 27% 10% 2	540
	11th to 20th	Day	15% 16% 32% 27% 9% 1	560
	21st to end	Day	17% 9% 28% 30% 16% 1	750
May	1st to 10th	Day	12% 9% 28% 31% 18% 3	753
	11th to 20th	Day	13% 9% 27% 27% 19% 5%	775
	21st to end	Day	15% 8% 24% 30% 17% 6%	844
June	1st to 10th	Day	14% 13% 29% 22% 16% 5%	780
	11th to 20th	Day	19% 11% 31% 25% 12% 3	780
	21st to end	Day	12% 8% 27% 29% 20% 4	780
July	1st to 10th	Day	8% 4 22% 36% 23% 7%	771
	11th to 20th	Day	9% 7% 26% 31% 21% 6%	768
	21st to end	Day	6% 6% 25% 35% 22% 8%	849
August	1st to 10th	Day	10% 6% 22% 35% 22% 5%	776
	11th to 20th	Day	9% 5% 22% 33% 25% 5%	765
	21st to end	Day	10% 7% 25% 30% 22% 5%	632
September	1st to 10th	Day	14% 9% 29% 28% 15% 4	570
	11th to 20th	Day	18% 9% 27% 28% 16% 2	560
	21st to end	Day	13% 10% 29% 32% 14% 2	360
October	1st to 10th	Day	16% 9% 30% 26% 16% 3	360
	11th to 20th	Day	16% 11% 35% 24% 14% 1	360
	21st to end	Day	15% 9% 37% 28% 9% 2	387
November	1st to 10th	Day	19% 10% 34% 23% 12% 3	330
	11th to 20th	Day	13% 12% 37% 29% 8%	330
	21st to end	Day	12% 10% 35% 30% 12% 1	330
December	1st to 10th	Day	14% 7% 37% 30% 11% 2	330
	11th to 20th	Day	14% 9% 48% 23% 5% 1	278
	21st to end	Day	12% 6% 36% 34% 10% 3	242
January	1st to 10th	Night	8% 8% 37% 34% 11% 2	1050
	11th to 20th	Night	13% 11% 35% 33% 7% 1	1050
	21st to end	Night	11% 10% 39% 30% 10% 1	1155
February	1st to 10th	Night	12% 8% 31% 34% 13% 1	1021
	11th to 20th	Night	9% 7% 33% 38% 12% 2	824
	21st to end	Night	5% 4 28% 39% 21% 3	692
March	1st to 10th	Night	10% 8% 34% 32% 14% 1	840
	11th to 20th	Night	11% 6% 36% 34% 12% 2	840
	21st to end	Night	14% 7% 31% 34% 13% 1	731
April	1st to 10th	Night	10% 7% 33% 37% 12% 1	630
	11th to 20th	Night	18% 8% 32% 33% 8% 1	623
	21st to end	Night	16% 9% 30% 37% 8%	630
May	1st to 10th	Night	13% 7% 27% 36% 16%	630
	11th to 20th	Night	16% 7% 28% 34% 14% 1	621
	21st to end	Night	18% 6% 27% 32% 15% 2	683
June	1st to 10th	Night	14% 6% 28% 35% 15% 1	479
	11th to 20th	Night	19% 5% 27% 35% 13%	420
	21st to end	Night	13% 5% 25% 38% 18% 1	420
July	1st to 10th	Night	9% 2 22% 46% 19% 2	410
	11th to 20th	Night	9% 2 26% 43% 19% 1	471
	21st to end	Night	6% 3 23% 43% 22% 2	690
August	1st to 10th	Night	7% 4 23% 41% 22% 2	627
	11th to 20th	Night	6% 3 20% 45% 24% 2	624
	21st to end	Night	10% 4 25% 39% 21% 1	693
September	1st to 10th	Night	10% 5% 25% 39% 19% 1	630
	11th to 20th	Night	12% 7% 25% 41% 15%	630
	21st to end	Night	12% 5% 32% 39% 11%	664
October	1st to 10th	Night	18% 5% 24% 37% 15% 1	840
	11th to 20th	Night	13% 7% 29% 37% 12% 1	906
	21st to end	Night	15% 10% 33% 33% 9% 1	1141
November	1st to 10th	Night	19% 10% 33% 31% 7%	1025
	11th to 20th	Night	15% 9% 34% 32% 8% 2	1050
	21st to end	Night	12% 8% 37% 34% 8% 1	1050
December	1st to 10th	Night	12% 7% 34% 33% 12% 2	1050
	11th to 20th	Night	13% 10% 34% 33% 9% 1	1050
	21st to end	Night	12% 4 32% 36% 13% 2	1155

Page generated at 2026-10-26 02:37:49. Version ac07

Copyright © 2026 Attilla Danko.