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 2024-04-03.

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% 4 7% 6% 4 5% 5% 6% 9% 35%	78243
	Night	7% 9% 4 8% 7% 4 6% 6% 6% 9% 34%	81845
Transparency	Day	44% 9% 16% 22% 8% 1	77945
	Night	45% 8% 15% 21% 9% 2	81723
Seeing	Day	12% 6% 25% 32% 19% 6%	14519
	Night	12% 5% 28% 37% 16% 2	23838

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 11% 6% 12% 8% 4 6% 5% 7% 8% 30%	2219
	11th to 20th	Day	5% 10% 4 9% 6% 5% 7% 9% 10% 8% 28%	2199
	21st to end	Day	5% 8% 4 10% 8% 4 6% 5% 7% 10% 33%	2729
February	1st to 10th	Day	8% 14% 5% 9% 7% 5% 6% 5% 6% 7% 28%	1520
	11th to 20th	Day	6% 12% 6% 10% 9% 5% 6% 7% 6% 8% 26%	1665
	21st to end	Day	4 11% 6% 11% 11% 5% 8% 5% 5% 8% 25%	1481
March	1st to 10th	Day	6% 12% 6% 11% 11% 5% 7% 5% 5% 6% 24%	1900
	11th to 20th	Day	7% 8% 5% 9% 8% 4 6% 6% 7% 8% 32%	2084
	21st to end	Day	9% 14% 7% 10% 6% 4 6% 5% 6% 7% 25%	2304
April	1st to 10th	Day	7% 10% 4 9% 7% 4 6% 6% 6% 10% 32%	2265
	11th to 20th	Day	12% 12% 4 8% 6% 3 6% 6% 7% 8% 28%	2310
	21st to end	Day	12% 9% 3 9% 7% 4 5% 5% 5% 9% 32%	2340
May	1st to 10th	Day	13% 11% 3 7% 7% 4 5% 6% 7% 9% 29%	2513
	11th to 20th	Day	9% 6% 2 6% 7% 4 6% 6% 7% 8% 40%	2654
	21st to end	Day	18% 7% 3 7% 6% 3 4 5% 6% 8% 33%	2917
June	1st to 10th	Day	16% 6% 2 5% 6% 4 6% 6% 8% 9% 32%	2700
	11th to 20th	Day	19% 7% 3 7% 7% 4 5% 6% 6% 8% 26%	2700
	21st to end	Day	8% 4 2 6% 6% 4 6% 6% 7% 10% 40%	2700
July	1st to 10th	Day	8% 6% 2 5% 5% 3 5% 6% 7% 10% 41%	2700
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 5% 7% 10% 43%	2700
	21st to end	Day	6% 4 2 4 4 3 4 5% 7% 10% 51%	2938
August	1st to 10th	Day	10% 5% 2 4 5% 3 5% 5% 7% 11% 44%	2516
	11th to 20th	Day	8% 4 2 4 4 3 4 5% 6% 10% 49%	2319
	21st to end	Day	10% 4 1 5% 4 3 4 6% 6% 8% 47%	2574
September	1st to 10th	Day	11% 6% 2 4 5% 3 4 5% 6% 8% 45%	2260
	11th to 20th	Day	15% 8% 3 5% 4 2 4 4 5% 8% 42%	1980
	21st to end	Day	8% 9% 3 5% 4 2 5% 5% 5% 9% 45%	1980
October	1st to 10th	Day	13% 11% 3 6% 5% 2 4 3 6% 7% 40%	1875
	11th to 20th	Day	9% 8% 4 7% 7% 4 5% 5% 6% 8% 37%	1684
	21st to end	Day	7% 12% 3 7% 7% 4 6% 6% 6% 7% 34%	1782
November	1st to 10th	Day	10% 15% 7% 10% 6% 3 5% 5% 6% 9% 24%	1502
	11th to 20th	Day	7% 13% 4 9% 7% 4 5% 4 5% 7% 34%	1449
	21st to end	Day	6% 11% 5% 10% 8% 5% 5% 5% 6% 8% 31%	1330
December	1st to 10th	Day	7% 11% 6% 10% 8% 7% 7% 6% 5% 6% 27%	1330
	11th to 20th	Day	4 11% 6% 12% 9% 5% 6% 6% 7% 8% 26%	1682
	21st to end	Day	4 8% 3 9% 7% 3 4 5% 6% 9% 41%	2442
January	1st to 10th	Night	4 12% 6% 11% 9% 5% 6% 6% 8% 9% 24%	4726
	11th to 20th	Night	4 8% 6% 11% 9% 5% 6% 7% 6% 8% 30%	4699
	21st to end	Night	4 11% 5% 9% 7% 4 5% 6% 7% 9% 32%	4958
February	1st to 10th	Night	7% 10% 6% 11% 8% 4 6% 6% 6% 8% 29%	2660
	11th to 20th	Night	5% 13% 5% 10% 8% 6% 7% 6% 7% 7% 26%	2402
	21st to end	Night	5% 9% 4 9% 10% 4 6% 6% 8% 9% 30%	1970
March	1st to 10th	Night	5% 10% 5% 10% 11% 6% 6% 5% 6% 8% 28%	2280
	11th to 20th	Night	7% 9% 5% 9% 8% 3 6% 6% 7% 9% 31%	2094
	21st to end	Night	8% 15% 5% 10% 7% 5% 6% 6% 7% 8% 22%	2293
April	1st to 10th	Night	9% 8% 4 7% 10% 4 6% 6% 6% 8% 31%	1740
	11th to 20th	Night	9% 11% 5% 10% 8% 4 6% 5% 6% 8% 28%	1601
	21st to end	Night	10% 10% 4 8% 6% 4 6% 6% 6% 8% 32%	1620
May	1st to 10th	Night	12% 11% 4 8% 7% 4 4 5% 6% 9% 29%	1443
	11th to 20th	Night	8% 7% 3 7% 7% 4 6% 5% 5% 8% 39%	1239
	21st to end	Night	19% 6% 4 6% 7% 4 4 4 6% 9% 33%	1358
June	1st to 10th	Night	15% 8% 4 7% 7% 4 5% 6% 8% 9% 28%	1260
	11th to 20th	Night	18% 8% 3 7% 8% 4 7% 7% 7% 7% 24%	1260
	21st to end	Night	10% 5% 2 6% 7% 3 5% 7% 7% 8% 39%	1260
July	1st to 10th	Night	9% 5% 2 6% 6% 3 5% 6% 9% 10% 42%	1260
	11th to 20th	Night	10% 5% 2 5% 5% 5% 5% 7% 8% 11% 37%	1260
	21st to end	Night	6% 4 2 4 4 2 5% 5% 7% 10% 50%	1379
August	1st to 10th	Night	9% 5% 2 5% 6% 4 5% 6% 6% 10% 42%	1422
	11th to 20th	Night	7% 5% 4 6% 5% 3 4 5% 7% 8% 44%	1581
	21st to end	Night	8% 4 2 6% 5% 3 5% 4 6% 10% 47%	1782
September	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 8% 46%	1697
	11th to 20th	Night	13% 6% 2 5% 6% 3 4 5% 5% 7% 43%	1980
	21st to end	Night	8% 6% 3 5% 5% 3 4 5% 7% 8% 47%	1980
October	1st to 10th	Night	11% 10% 3 5% 5% 3 4 6% 5% 7% 40%	2085
	11th to 20th	Night	9% 8% 4 8% 6% 3 6% 4 6% 9% 38%	2272
	21st to end	Night	7% 9% 4 8% 7% 4 6% 6% 6% 9% 34%	2574
November	1st to 10th	Night	11% 13% 5% 8% 5% 4 6% 4 6% 8% 31%	2558
	11th to 20th	Night	5% 9% 5% 10% 8% 5% 7% 6% 7% 8% 31%	2728
	21st to end	Night	5% 9% 4 10% 8% 5% 6% 5% 7% 10% 32%	2850
December	1st to 10th	Night	6% 11% 6% 11% 8% 5% 5% 4 5% 9% 30%	2850
	11th to 20th	Night	3 9% 5% 11% 10% 5% 8% 6% 6% 9% 29%	3510
	21st to end	Night	4 8% 4 7% 6% 4 5% 5% 6% 9% 43%	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	50% 7% 14% 20% 9% 1	2219
	11th to 20th	Day	46% 8% 14% 15% 15% 2	2220
	21st to end	Day	42% 9% 17% 26% 7%	2729
February	1st to 10th	Day	53% 6% 15% 16% 10% 1	1520
	11th to 20th	Day	54% 9% 13% 15% 8% 1	1674
	21st to end	Day	56% 7% 10% 18% 9%	1481
March	1st to 10th	Day	58% 9% 13% 14% 6%	1900
	11th to 20th	Day	46% 9% 13% 22% 10%	2085
	21st to end	Day	56% 8% 15% 14% 6%	2304
April	1st to 10th	Day	46% 10% 17% 18% 8% 1	2265
	11th to 20th	Day	50% 7% 14% 21% 8% 1	2310
	21st to end	Day	49% 7% 15% 22% 6% 2	2340
May	1st to 10th	Day	49% 9% 15% 20% 7%	2513
	11th to 20th	Day	38% 9% 15% 26% 11% 1	2658
	21st to end	Day	48% 8% 15% 21% 8% 1	2918
June	1st to 10th	Day	45% 10% 17% 21% 8%	2700
	11th to 20th	Day	53% 10% 13% 19% 4 1	2700
	21st to end	Day	35% 12% 20% 26% 6% 1	2700
July	1st to 10th	Day	35% 11% 21% 25% 7% 1	2626
	11th to 20th	Day	36% 10% 21% 28% 5%	2619
	21st to end	Day	26% 10% 23% 30% 9%	2775
August	1st to 10th	Day	33% 11% 22% 27% 7% 1	2498
	11th to 20th	Day	30% 10% 25% 25% 9% 1	2319
	21st to end	Day	31% 10% 21% 26% 11% 1	2574
September	1st to 10th	Day	35% 9% 18% 26% 9% 3	2260
	11th to 20th	Day	40% 6% 14% 29% 9% 1	1980
	21st to end	Day	35% 8% 18% 25% 11% 3	1980
October	1st to 10th	Day	43% 6% 17% 23% 9% 1	1875
	11th to 20th	Day	43% 7% 18% 22% 10% 1	1684
	21st to end	Day	46% 8% 13% 21% 11% 1	1782
November	1st to 10th	Day	55% 7% 14% 16% 6% 1	1502
	11th to 20th	Day	49% 8% 13% 21% 8% 1	1449
	21st to end	Day	49% 8% 16% 18% 8% 1	1330
December	1st to 10th	Day	56% 7% 13% 14% 8% 2	1330
	11th to 20th	Day	52% 10% 14% 19% 4 1	1684
	21st to end	Day	38% 6% 13% 24% 16% 4	2442
January	1st to 10th	Night	52% 9% 12% 19% 6% 2	4726
	11th to 20th	Night	50% 7% 12% 16% 13% 3	4740
	21st to end	Night	45% 9% 15% 22% 8% 1	4958
February	1st to 10th	Night	52% 7% 12% 19% 10%	2660
	11th to 20th	Night	52% 8% 13% 15% 10% 2	2403
	21st to end	Night	46% 9% 13% 20% 11% 1	1970
March	1st to 10th	Night	52% 8% 14% 19% 6% 1	2280
	11th to 20th	Night	46% 7% 16% 21% 9% 1	2094
	21st to end	Night	56% 9% 14% 15% 6% 1	2293
April	1st to 10th	Night	48% 10% 14% 17% 11%	1740
	11th to 20th	Night	51% 7% 13% 22% 7% 1	1601
	21st to end	Night	47% 9% 13% 22% 7% 2	1620
May	1st to 10th	Night	49% 7% 14% 20% 9% 1	1443
	11th to 20th	Night	42% 8% 12% 22% 16%	1239
	21st to end	Night	48% 8% 14% 22% 7% 1	1358
June	1st to 10th	Night	49% 10% 14% 18% 9%	1260
	11th to 20th	Night	56% 9% 13% 15% 5% 1	1260
	21st to end	Night	38% 11% 18% 24% 7% 1	1260
July	1st to 10th	Night	33% 13% 22% 25% 6% 1	1225
	11th to 20th	Night	36% 14% 21% 20% 8%	1218
	21st to end	Night	26% 10% 23% 29% 10% 1	1302
August	1st to 10th	Night	35% 13% 20% 24% 7% 1	1415
	11th to 20th	Night	35% 9% 18% 28% 9% 1	1581
	21st to end	Night	31% 8% 19% 28% 11% 2	1782
September	1st to 10th	Night	33% 8% 17% 25% 12% 4	1697
	11th to 20th	Night	39% 8% 14% 25% 10% 4	1980
	21st to end	Night	33% 7% 17% 27% 14% 2	1980
October	1st to 10th	Night	42% 7% 15% 25% 11% 1	2085
	11th to 20th	Night	42% 6% 17% 22% 9% 2	2272
	21st to end	Night	45% 10% 15% 21% 8% 1	2574
November	1st to 10th	Night	50% 7% 12% 21% 8% 1	2558
	11th to 20th	Night	48% 9% 14% 18% 10% 1	2728
	21st to end	Night	46% 9% 18% 18% 7% 2	2850
December	1st to 10th	Night	52% 7% 10% 20% 9% 2	2850
	11th to 20th	Night	50% 10% 16% 18% 6%	3507
	21st to end	Night	37% 7% 13% 24% 16% 4	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	6% 4 27% 36% 19% 9%	180
	11th to 20th	Day	8% 4 34% 30% 20% 3	180
	21st to end	Day	6% 8% 29% 29% 21% 7%	198
February	1st to 10th	Day	11% 10% 24% 36% 13% 7%	180
	11th to 20th	Day	12% 6% 25% 36% 17% 4	270
	21st to end	Day	8% 6% 25% 36% 19% 6%	293
March	1st to 10th	Day	9% 6% 29% 34% 17% 5%	460
	11th to 20th	Day	7% 4 26% 36% 20% 7%	460
	21st to end	Day	13% 6% 28% 30% 18% 6%	506
April	1st to 10th	Day	9% 11% 30% 31% 13% 6%	429
	11th to 20th	Day	15% 8% 30% 28% 15% 5%	412
	21st to end	Day	17% 9% 27% 31% 13% 3	420
May	1st to 10th	Day	16% 10% 23% 27% 17% 6%	519
	11th to 20th	Day	13% 6% 21% 35% 21% 4	625
	21st to end	Day	18% 5% 21% 27% 22% 7%	679
June	1st to 10th	Day	16% 6% 26% 35% 14% 3	630
	11th to 20th	Day	20% 7% 25% 30% 14% 4	630
	21st to end	Day	9% 4 23% 30% 26% 8%	630
July	1st to 10th	Day	11% 4 19% 36% 23% 8%	621
	11th to 20th	Day	12% 5% 19% 35% 23% 6%	618
	21st to end	Day	6% 2 19% 36% 27% 10%	684
August	1st to 10th	Day	9% 5% 25% 31% 20% 10%	456
	11th to 20th	Day	8% 6% 21% 31% 29% 5%	437
	21st to end	Day	10% 7% 22% 29% 23% 9%	495
September	1st to 10th	Day	15% 6% 29% 29% 18% 3	450
	11th to 20th	Day	18% 6% 22% 29% 20% 4	450
	21st to end	Day	13% 12% 28% 29% 14% 5%	450
October	1st to 10th	Day	20% 6% 22% 28% 17% 6%	345
	11th to 20th	Day	11% 10% 34% 26% 16% 4	270
	21st to end	Day	14% 13% 33% 27% 13%	297
November	1st to 10th	Day	20% 7% 25% 33% 12% 3	270
	11th to 20th	Day	16% 7% 30% 31% 14% 2	237
	21st to end	Day	8% 6% 30% 33% 16% 7%	180
December	1st to 10th	Day	11% 2 28% 34% 21% 4	180
	11th to 20th	Day	6% 6% 34% 37% 14% 3	180
	21st to end	Day	10% 3 21% 38% 22% 7%	198
January	1st to 10th	Night	12% 6% 31% 35% 15% 2	950
	11th to 20th	Night	11% 6% 31% 36% 14% 1	950
	21st to end	Night	11% 8% 29% 37% 12% 2	893
February	1st to 10th	Night	12% 6% 26% 35% 18% 3	760
	11th to 20th	Night	11% 5% 31% 36% 16% 1	744
	21st to end	Night	7% 4 24% 41% 19% 5%	628
March	1st to 10th	Night	9% 5% 27% 40% 16% 4	760
	11th to 20th	Night	9% 5% 29% 38% 16% 3	760
	21st to end	Night	13% 5% 26% 35% 18% 2	836
April	1st to 10th	Night	12% 6% 29% 33% 17% 2	648
	11th to 20th	Night	15% 6% 31% 36% 11% 1	533
	21st to end	Night	15% 9% 27% 34% 14% 1	540
May	1st to 10th	Night	16% 7% 26% 36% 13% 1	460
	11th to 20th	Night	12% 5% 27% 39% 16% 2	354
	21st to end	Night	19% 6% 23% 32% 18% 1	389
June	1st to 10th	Night	17% 7% 24% 35% 14% 3	360
	11th to 20th	Night	20% 4 28% 31% 17% 1	360
	21st to end	Night	13% 3 22% 39% 21% 2	360
July	1st to 10th	Night	11% 3 17% 45% 23% 1	350
	11th to 20th	Night	14% 3 19% 42% 20% 2	348
	21st to end	Night	7% 3 20% 41% 27% 3	394
August	1st to 10th	Night	13% 2 18% 38% 26% 3	358
	11th to 20th	Night	9% 5% 17% 43% 24% 1	513
	21st to end	Night	8% 5% 19% 44% 23%	594
September	1st to 10th	Night	12% 3 24% 41% 19% 2	586
	11th to 20th	Night	14% 5% 22% 39% 20% 1	720
	21st to end	Night	11% 4 27% 38% 17% 2	720
October	1st to 10th	Night	15% 5% 25% 36% 18% 2	720
	11th to 20th	Night	11% 5% 31% 35% 16% 2	720
	21st to end	Night	13% 7% 31% 35% 13% 1	792
November	1st to 10th	Night	16% 8% 29% 35% 10% 1	893
	11th to 20th	Night	8% 7% 38% 34% 10% 2	950
	21st to end	Night	9% 5% 35% 38% 13% 2	950
December	1st to 10th	Night	11% 6% 29% 35% 16% 2	950
	11th to 20th	Night	9% 5% 34% 37% 12% 2	950
	21st to end	Night	11% 4 30% 37% 15% 2	1045

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