Wyrd Works
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wyrd Works 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	8% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	154675
	Night	7% 9% 4 10% 6% 5% 6% 4 7% 8% 34%	146140
Transparency	Day	41% 7% 16% 25% 9% 1	154372
	Night	44% 8% 16% 22% 9% 1	146026
Seeing	Day	12% 7% 25% 32% 19% 6%	18055
	Night	11% 6% 28% 37% 16% 2	27001

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% 6% 16% 8% 7% 6% 3 6% 6% 27%	4125
	11th to 20th	Day	3 8% 4 10% 6% 7% 6% 6% 8% 9% 33%	4119
	21st to end	Day	3 9% 4 11% 6% 5% 5% 4 6% 9% 38%	5065
February	1st to 10th	Day	7% 14% 4 11% 6% 7% 6% 4 6% 7% 28%	1680
	11th to 20th	Day	6% 13% 4 11% 7% 7% 5% 5% 7% 8% 26%	1845
	21st to end	Day	4 13% 4 12% 9% 8% 8% 4 6% 8% 26%	1633
March	1st to 10th	Day	3 10% 5% 11% 8% 6% 6% 4 7% 9% 31%	4618
	11th to 20th	Day	5% 12% 4 10% 6% 5% 4 4 6% 8% 35%	5104
	21st to end	Day	10% 19% 7% 14% 5% 5% 5% 4 5% 6% 21%	5623
April	1st to 10th	Day	8% 12% 3 10% 6% 5% 5% 5% 6% 9% 31%	2615
	11th to 20th	Day	11% 12% 4 9% 5% 4 6% 5% 7% 9% 29%	2700
	21st to end	Day	12% 10% 3 10% 5% 5% 5% 4 6% 8% 32%	2730
May	1st to 10th	Day	12% 8% 3 6% 4 4 5% 4 7% 8% 39%	8216
	11th to 20th	Day	12% 11% 3 9% 5% 6% 6% 5% 7% 8% 28%	8755
	21st to end	Day	12% 6% 3 8% 5% 5% 5% 4 7% 8% 37%	9649
June	1st to 10th	Day	16% 6% 2 6% 5% 5% 6% 5% 7% 8% 33%	3150
	11th to 20th	Day	18% 8% 3 8% 7% 6% 6% 5% 6% 8% 27%	3150
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 5% 8% 10% 40%	3150
July	1st to 10th	Day	6% 5% 2 5% 4 4 4 4 6% 9% 50%	8820
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 7% 9% 44%	8820
	21st to end	Day	7% 4 2 5% 4 3 4 4 6% 9% 53%	9569
August	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 4 6% 10% 45%	6450
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 4 7% 10% 40%	5971
	21st to end	Day	8% 4 1 5% 3 4 4 4 6% 8% 53%	6570
September	1st to 10th	Day	11% 6% 2 5% 4 4 4 4 6% 8% 46%	2635
	11th to 20th	Day	14% 8% 2 5% 3 3 4 3 5% 8% 45%	2310
	21st to end	Day	8% 8% 2 5% 3 4 4 5% 6% 9% 46%	2310
October	1st to 10th	Day	7% 7% 2 6% 5% 5% 6% 4 7% 8% 43%	3509
	11th to 20th	Day	6% 7% 3 8% 5% 5% 4 4 7% 10% 41%	3132
	21st to end	Day	8% 9% 3 7% 6% 5% 5% 4 6% 7% 41%	3272
November	1st to 10th	Day	9% 15% 6% 10% 6% 5% 4 5% 6% 9% 25%	1662
	11th to 20th	Day	6% 14% 4 11% 6% 5% 5% 4 6% 6% 33%	1601
	21st to end	Day	6% 13% 3 11% 8% 6% 6% 4 6% 8% 29%	1470
December	1st to 10th	Day	9% 12% 4 10% 6% 7% 6% 5% 6% 8% 26%	2360
	11th to 20th	Day	7% 11% 5% 13% 10% 7% 5% 5% 6% 7% 25%	2712
	21st to end	Day	3 7% 4 11% 6% 5% 5% 4 6% 9% 41%	3575
January	1st to 10th	Night	5% 13% 6% 15% 8% 7% 6% 4 6% 7% 23%	8768
	11th to 20th	Night	3 8% 4 11% 6% 5% 6% 5% 7% 9% 36%	8779
	21st to end	Night	3 9% 4 11% 6% 6% 6% 5% 7% 9% 35%	9174
February	1st to 10th	Night	6% 11% 5% 12% 7% 6% 6% 5% 6% 8% 28%	2939
	11th to 20th	Night	5% 13% 4 12% 7% 7% 7% 5% 8% 7% 26%	2662
	21st to end	Night	4 11% 3 11% 8% 6% 7% 4 8% 9% 29%	2170
March	1st to 10th	Night	3 8% 4 12% 9% 7% 6% 5% 6% 9% 30%	5496
	11th to 20th	Night	5% 8% 4 11% 6% 6% 6% 6% 9% 9% 29%	5114
	21st to end	Night	7% 18% 6% 16% 6% 6% 6% 4 6% 6% 18%	5580
April	1st to 10th	Night	10% 10% 3 8% 8% 6% 5% 5% 6% 8% 31%	2005
	11th to 20th	Night	8% 11% 5% 12% 6% 6% 7% 4 6% 7% 28%	1871
	21st to end	Night	9% 11% 4 10% 5% 6% 5% 5% 6% 7% 32%	1890
May	1st to 10th	Night	13% 9% 3 8% 5% 4 5% 4 6% 7% 36%	4715
	11th to 20th	Night	11% 9% 3 9% 7% 6% 6% 5% 7% 9% 27%	4105
	21st to end	Night	12% 7% 3 8% 7% 6% 5% 5% 6% 9% 33%	4522
June	1st to 10th	Night	15% 9% 3 8% 7% 5% 5% 5% 7% 9% 27%	1470
	11th to 20th	Night	16% 9% 3 8% 8% 7% 6% 6% 7% 6% 24%	1470
	21st to end	Night	11% 5% 1 7% 6% 5% 5% 6% 7% 8% 38%	1470
July	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 5% 8% 9% 47%	4140
	11th to 20th	Night	8% 4 2 5% 4 4 4 4 7% 9% 48%	4140
	21st to end	Night	7% 5% 2 5% 4 4 4 4 6% 11% 48%	4499
August	1st to 10th	Night	10% 8% 3 7% 4 3 4 4 5% 7% 45%	3685
	11th to 20th	Night	9% 6% 3 8% 5% 5% 6% 5% 8% 9% 35%	4092
	21st to end	Night	6% 4 2 6% 4 5% 5% 4 7% 10% 47%	4578
September	1st to 10th	Night	10% 5% 3 6% 3 4 4 3 6% 8% 46%	1982
	11th to 20th	Night	12% 6% 2 6% 4 4 5% 3 5% 7% 45%	2310
	21st to end	Night	8% 6% 3 6% 4 3 4 4 7% 8% 48%	2310
October	1st to 10th	Night	7% 7% 2 6% 4 4 5% 5% 6% 9% 45%	3905
	11th to 20th	Night	7% 8% 3 7% 4 5% 5% 3 7% 9% 43%	4231
	21st to end	Night	6% 8% 3 8% 5% 5% 5% 5% 7% 7% 39%	4704
November	1st to 10th	Night	10% 14% 4 9% 4 6% 5% 3 6% 8% 30%	2835
	11th to 20th	Night	5% 10% 5% 11% 7% 6% 7% 4 7% 8% 30%	3016
	21st to end	Night	5% 11% 4 11% 8% 6% 5% 4 7% 9% 30%	3150
December	1st to 10th	Night	7% 13% 5% 12% 7% 7% 6% 4 6% 8% 25%	5040
	11th to 20th	Night	6% 12% 5% 14% 9% 6% 7% 5% 7% 8% 21%	5700
	21st to end	Night	3 7% 4 9% 6% 5% 6% 4 6% 9% 40%	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	56% 5% 10% 18% 11% 1	4125
	11th to 20th	Day	43% 6% 15% 17% 16% 3	4140
	21st to end	Day	40% 6% 17% 28% 8%	5066
February	1st to 10th	Day	53% 6% 14% 16% 11% 1	1680
	11th to 20th	Day	52% 8% 12% 17% 10% 1	1854
	21st to end	Day	54% 7% 10% 20% 9%	1633
March	1st to 10th	Day	47% 6% 17% 20% 10%	4618
	11th to 20th	Day	44% 8% 13% 22% 12%	5105
	21st to end	Day	62% 7% 10% 15% 6%	5623
April	1st to 10th	Day	47% 9% 17% 19% 8% 1	2615
	11th to 20th	Day	48% 7% 14% 21% 8% 1	2700
	21st to end	Day	48% 7% 13% 23% 6% 1	2730
May	1st to 10th	Day	39% 6% 11% 30% 12% 2	8216
	11th to 20th	Day	47% 9% 13% 23% 8% 1	8759
	21st to end	Day	41% 9% 17% 25% 8%	9650
June	1st to 10th	Day	44% 9% 16% 21% 9% 1	3150
	11th to 20th	Day	52% 10% 13% 20% 5% 1	3150
	21st to end	Day	36% 11% 20% 27% 6% 1	3150
July	1st to 10th	Day	28% 8% 20% 33% 11% 1	8746
	11th to 20th	Day	33% 7% 19% 28% 10% 2	8739
	21st to end	Day	27% 7% 18% 30% 15% 2	9362
August	1st to 10th	Day	32% 8% 18% 31% 9% 2	6432
	11th to 20th	Day	36% 9% 23% 26% 5%	6010
	21st to end	Day	27% 7% 20% 35% 10% 1	6569
September	1st to 10th	Day	35% 8% 17% 27% 10% 3	2635
	11th to 20th	Day	38% 6% 14% 30% 10% 1	2310
	21st to end	Day	34% 8% 18% 26% 11% 3	2310
October	1st to 10th	Day	37% 6% 21% 28% 7% 1	3509
	11th to 20th	Day	37% 6% 18% 26% 11% 2	3132
	21st to end	Day	42% 6% 10% 33% 9% 1	3272
November	1st to 10th	Day	55% 7% 14% 17% 6% 2	1662
	11th to 20th	Day	49% 8% 13% 21% 8% 1	1601
	21st to end	Day	52% 8% 15% 17% 7% 1	1470
December	1st to 10th	Day	55% 6% 18% 16% 5% 1	2360
	11th to 20th	Day	56% 8% 15% 17% 3 1	2714
	21st to end	Day	38% 5% 13% 26% 15% 3	3575
January	1st to 10th	Night	58% 6% 11% 16% 8% 1	8769
	11th to 20th	Night	43% 6% 16% 19% 13% 3	8820
	21st to end	Night	43% 7% 19% 23% 7%	9174
February	1st to 10th	Night	52% 7% 12% 19% 11%	2939
	11th to 20th	Night	52% 8% 12% 16% 11% 2	2663
	21st to end	Night	46% 8% 13% 20% 11% 1	2170
March	1st to 10th	Night	46% 8% 18% 19% 8%	5496
	11th to 20th	Night	44% 8% 18% 23% 7% 1	5114
	21st to end	Night	62% 8% 10% 13% 6% 1	5580
April	1st to 10th	Night	48% 10% 14% 18% 11%	2005
	11th to 20th	Night	51% 7% 12% 22% 7% 1	1871
	21st to end	Night	47% 9% 12% 23% 8% 2	1890
May	1st to 10th	Night	45% 7% 9% 25% 13% 2	4712
	11th to 20th	Night	48% 9% 14% 21% 8%	4105
	21st to end	Night	45% 10% 16% 23% 6%	4526
June	1st to 10th	Night	49% 10% 13% 17% 9% 1	1470
	11th to 20th	Night	55% 9% 13% 16% 5% 1	1470
	21st to end	Night	39% 10% 19% 24% 7% 1	1470
July	1st to 10th	Night	28% 11% 21% 29% 10% 1	4105
	11th to 20th	Night	30% 8% 20% 31% 8% 3	4098
	21st to end	Night	29% 8% 20% 28% 13% 2	4401
August	1st to 10th	Night	38% 7% 16% 30% 9%	3678
	11th to 20th	Night	40% 10% 22% 24% 4 1	4119
	21st to end	Night	30% 7% 21% 34% 7% 1	4578
September	1st to 10th	Night	33% 8% 16% 25% 13% 5%	1982
	11th to 20th	Night	37% 7% 14% 28% 11% 3	2310
	21st to end	Night	32% 7% 16% 28% 15% 2	2310
October	1st to 10th	Night	34% 7% 20% 28% 11% 1	3905
	11th to 20th	Night	37% 5% 17% 30% 9% 2	4231
	21st to end	Night	40% 8% 15% 29% 8% 1	4704
November	1st to 10th	Night	50% 7% 12% 21% 8% 1	2835
	11th to 20th	Night	49% 8% 14% 18% 10% 1	3016
	21st to end	Night	48% 9% 17% 18% 7% 2	3150
December	1st to 10th	Night	56% 7% 15% 16% 5% 1	5040
	11th to 20th	Night	57% 9% 15% 14% 5%	5697
	21st to end	Night	39% 6% 12% 24% 17% 3	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	7% 5% 27% 35% 19% 8%	220
	11th to 20th	Day	8% 7% 35% 30% 17% 2	220
	21st to end	Day	6% 9% 30% 30% 20% 6%	242
February	1st to 10th	Day	9% 10% 25% 35% 14% 7%	220
	11th to 20th	Day	11% 5% 25% 37% 18% 3	330
	21st to end	Day	7% 7% 27% 35% 19% 5%	349
March	1st to 10th	Day	8% 6% 29% 34% 18% 5%	540
	11th to 20th	Day	8% 4 27% 37% 18% 6%	540
	21st to end	Day	13% 6% 28% 30% 16% 5%	594
April	1st to 10th	Day	11% 12% 28% 30% 13% 6%	540
	11th to 20th	Day	14% 9% 32% 27% 14% 4	532
	21st to end	Day	17% 10% 26% 31% 13% 4	540
May	1st to 10th	Day	16% 11% 25% 27% 17% 5%	656
	11th to 20th	Day	13% 9% 21% 33% 20% 4	775
	21st to end	Day	16% 5% 21% 28% 22% 7%	844
June	1st to 10th	Day	16% 8% 26% 33% 13% 4	780
	11th to 20th	Day	18% 8% 24% 30% 14% 5%	780
	21st to end	Day	11% 4 22% 30% 25% 8%	780
July	1st to 10th	Day	11% 4 18% 36% 24% 8%	771
	11th to 20th	Day	11% 5% 20% 34% 23% 6%	768
	21st to end	Day	7% 3 19% 35% 26% 10%	849
August	1st to 10th	Day	8% 6% 25% 30% 21% 9%	576
	11th to 20th	Day	7% 6% 22% 32% 27% 6%	557
	21st to end	Day	9% 7% 21% 31% 23% 8%	627
September	1st to 10th	Day	15% 5% 26% 29% 20% 5%	570
	11th to 20th	Day	17% 6% 20% 29% 22% 6%	570
	21st to end	Day	12% 12% 30% 28% 14% 4	570
October	1st to 10th	Day	16% 6% 24% 32% 17% 5%	447
	11th to 20th	Day	10% 11% 36% 26% 14% 4	360
	21st to end	Day	14% 13% 31% 29% 12% 1	387
November	1st to 10th	Day	19% 7% 27% 33% 11% 3	330
	11th to 20th	Day	13% 7% 33% 31% 14% 2	289
	21st to end	Day	10% 6% 28% 35% 15% 6%	220
December	1st to 10th	Day	12% 4 28% 34% 19% 4	220
	11th to 20th	Day	8% 8% 33% 35% 13% 3	220
	21st to end	Day	9% 3 21% 37% 22% 7%	242
January	1st to 10th	Night	12% 6% 31% 35% 15% 2	1050
	11th to 20th	Night	11% 7% 33% 35% 13% 1	1050
	21st to end	Night	11% 8% 30% 37% 11% 2	987
February	1st to 10th	Night	11% 6% 27% 36% 17% 2	840
	11th to 20th	Night	10% 5% 32% 37% 15% 1	824
	21st to end	Night	7% 4 24% 41% 18% 5%	692
March	1st to 10th	Night	8% 5% 28% 40% 16% 3	840
	11th to 20th	Night	8% 5% 30% 38% 15% 3	840
	21st to end	Night	13% 5% 27% 35% 17% 2	924
April	1st to 10th	Night	13% 7% 29% 33% 16% 2	745
	11th to 20th	Night	13% 7% 33% 35% 10% 1	623
	21st to end	Night	14% 9% 27% 34% 15% 1	630
May	1st to 10th	Night	16% 8% 27% 36% 12% 1	536
	11th to 20th	Night	11% 6% 28% 38% 15% 1	414
	21st to end	Night	18% 7% 23% 32% 19% 1	455
June	1st to 10th	Night	17% 7% 27% 34% 12% 2	420
	11th to 20th	Night	19% 4 29% 31% 17%	420
	21st to end	Night	14% 4 22% 39% 20% 2	420
July	1st to 10th	Night	10% 3 17% 47% 21% 1	410
	11th to 20th	Night	13% 3 19% 43% 19% 2	408
	21st to end	Night	7% 3 19% 42% 27% 2	460
August	1st to 10th	Night	12% 3 18% 38% 24% 4	418
	11th to 20th	Night	9% 5% 18% 44% 24% 1	600
	21st to end	Night	8% 6% 20% 45% 21%	693
September	1st to 10th	Night	12% 3 23% 42% 19% 1	685
	11th to 20th	Night	13% 5% 20% 40% 21% 1	840
	21st to end	Night	11% 5% 28% 39% 15% 2	840
October	1st to 10th	Night	14% 5% 25% 37% 17% 1	840
	11th to 20th	Night	11% 6% 32% 36% 14% 2	840
	21st to end	Night	12% 8% 30% 36% 13% 1	912
November	1st to 10th	Night	15% 8% 30% 36% 9% 1	990
	11th to 20th	Night	8% 8% 37% 35% 10% 2	1050
	21st to end	Night	9% 5% 34% 38% 13% 2	1050
December	1st to 10th	Night	12% 7% 31% 33% 15% 2	1050
	11th to 20th	Night	9% 6% 35% 36% 12% 2	1050
	21st to end	Night	11% 5% 30% 37% 15% 2	1155

Page generated at 2026-10-26 02:37:51. Version ac07

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