Carnation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carnation clear sky chart from 2005-11-06 to 2025-04-11.

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	23% 10% 3 7% 5% 4 4 3 5% 6% 31%	117882
	Night	26% 11% 3 7% 4 4 4 3 4 5% 29%	119010
Transparency	Day	55% 6% 13% 17% 8% 1	117641
	Night	58% 6% 12% 15% 7% 1	118897
Seeing	Day	28% 9% 19% 26% 14% 3	15439
	Night	33% 7% 13% 26% 18% 2	23974

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	40% 15% 3 8% 4 4 4 3 4 5% 10%	3477
	11th to 20th	Day	21% 11% 3 8% 5% 5% 5% 3 5% 6% 28%	3616
	21st to end	Day	33% 9% 3 6% 3 3 3 2 3 4 30%	4073
February	1st to 10th	Day	32% 12% 3 8% 6% 5% 4 3 4 6% 16%	1800
	11th to 20th	Day	32% 14% 4 8% 4 4 4 3 3 4 20%	1755
	21st to end	Day	30% 16% 4 8% 4 4 3 3 4 4 19%	1569
March	1st to 10th	Day	22% 14% 4 9% 6% 5% 5% 4 6% 6% 19%	4579
	11th to 20th	Day	20% 15% 4 9% 6% 5% 5% 3 4 4 26%	5000
	21st to end	Day	28% 13% 4 9% 6% 6% 6% 5% 6% 6% 13%	5700
April	1st to 10th	Day	27% 14% 3 9% 6% 5% 5% 4 5% 6% 16%	2400
	11th to 20th	Day	24% 12% 4 8% 7% 4 5% 4 4 5% 24%	2258
	21st to end	Day	26% 11% 3 10% 6% 5% 5% 4 5% 5% 20%	2532
May	1st to 10th	Day	21% 9% 3 6% 5% 4 4 4 5% 5% 35%	4420
	11th to 20th	Day	21% 7% 2 6% 4 3 4 3 5% 9% 35%	4377
	21st to end	Day	33% 11% 3 8% 6% 4 4 3 4 6% 19%	4813
June	1st to 10th	Day	26% 9% 2 7% 5% 5% 5% 4 5% 6% 25%	2662
	11th to 20th	Day	28% 10% 3 8% 6% 5% 6% 4 5% 6% 20%	2850
	21st to end	Day	14% 7% 3 8% 5% 4 5% 4 6% 6% 37%	2850
July	1st to 10th	Day	9% 4 1 5% 3 2 3 3 4 5% 62%	4740
	11th to 20th	Day	7% 4 1 4 3 3 2 3 4 5% 65%	4462
	21st to end	Day	14% 5% 1 4 3 2 3 3 4 6% 56%	4790
August	1st to 10th	Day	7% 3 1 3 3 3 3 3 5% 7% 60%	4358
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 7% 8% 38%	4026
	21st to end	Day	18% 7% 3 7% 4 4 4 3 4 7% 41%	4309
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 3 5% 7% 49%	2280
	11th to 20th	Day	17% 8% 3 7% 5% 4 4 4 5% 7% 37%	2280
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 5% 38%	2017
October	1st to 10th	Day	18% 7% 3 5% 3 3 5% 4 6% 9% 37%	3180
	11th to 20th	Day	31% 9% 3 7% 4 4 4 3 4 7% 25%	3161
	21st to end	Day	29% 9% 3 10% 6% 5% 5% 3 5% 6% 19%	3227
November	1st to 10th	Day	39% 10% 3 7% 4 4 4 5% 4 5% 17%	1630
	11th to 20th	Day	37% 10% 3 7% 4 4 4 3 4 4 20%	1600
	21st to end	Day	35% 11% 3 7% 5% 3 4 3 4 5% 20%	1600
December	1st to 10th	Day	25% 8% 2 6% 4 5% 4 4 6% 5% 31%	2620
	11th to 20th	Day	32% 14% 4 9% 6% 4 4 3 4 4 14%	3025
	21st to end	Day	33% 14% 4 10% 6% 5% 4 3 4 4 14%	3846
January	1st to 10th	Night	38% 14% 4 9% 5% 5% 4 3 4 4 10%	6422
	11th to 20th	Night	22% 10% 3 7% 4 3 4 4 5% 7% 30%	6282
	21st to end	Night	30% 8% 3 6% 4 3 4 3 3 5% 31%	6883
February	1st to 10th	Night	34% 12% 4 8% 4 4 4 3 4 5% 18%	2600
	11th to 20th	Night	31% 14% 3 7% 4 4 3 3 3 5% 22%	2532
	21st to end	Night	33% 15% 3 7% 4 3 3 3 4 6% 19%	2060
March	1st to 10th	Night	20% 15% 3 8% 5% 5% 5% 5% 6% 7% 20%	5300
	11th to 20th	Night	25% 13% 3 8% 4 4 3 3 4 5% 29%	4999
	21st to end	Night	34% 14% 3 8% 5% 5% 4 4 5% 4 14%	5275
April	1st to 10th	Night	28% 12% 3 9% 6% 4 5% 5% 6% 6% 18%	2000
	11th to 20th	Night	23% 12% 4 8% 5% 4 4 3 5% 5% 27%	1878
	21st to end	Night	29% 10% 3 7% 5% 4 4 3 5% 7% 22%	1648
May	1st to 10th	Night	23% 9% 2 7% 4 3 3 2 3 4 39%	2540
	11th to 20th	Night	21% 9% 3 6% 4 4 3 3 4 7% 37%	2516
	21st to end	Night	33% 12% 4 9% 5% 4 4 2 4 4 19%	2762
June	1st to 10th	Night	23% 9% 3 8% 6% 4 4 4 5% 5% 30%	1513
	11th to 20th	Night	27% 10% 3 9% 6% 4 5% 3 4 5% 24%	1330
	21st to end	Night	14% 7% 2 7% 5% 4 4 4 5% 6% 42%	1330
July	1st to 10th	Night	11% 5% 2 5% 3 2 2 2 3 3 61%	2220
	11th to 20th	Night	6% 3 1 3 3 2 2 2 3 4 72%	2494
	21st to end	Night	14% 6% 2 3 3 2 3 2 3 6% 56%	2762
August	1st to 10th	Night	5% 3 1 3 2 2 3 3 4 6% 67%	2558
	11th to 20th	Night	15% 8% 3 6% 4 3 3 2 4 5% 47%	2812
	21st to end	Night	19% 8% 2 6% 3 2 3 2 3 4 47%	3365
September	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 6% 53%	1900
	11th to 20th	Night	20% 8% 2 7% 3 3 4 3 4 5% 41%	1900
	21st to end	Night	20% 7% 2 7% 4 4 4 3 4 5% 40%	2161
October	1st to 10th	Night	19% 7% 2 6% 4 3 4 3 6% 8% 38%	3800
	11th to 20th	Night	29% 8% 2 6% 4 4 4 3 5% 5% 29%	3777
	21st to end	Night	29% 13% 3 9% 5% 4 4 3 4 5% 22%	4335
November	1st to 10th	Night	35% 11% 3 6% 4 4 4 3 5% 5% 20%	2666
	11th to 20th	Night	36% 11% 3 7% 5% 3 3 2 4 4 21%	2800
	21st to end	Night	33% 11% 3 7% 4 4 4 3 3 5% 21%	2800
December	1st to 10th	Night	24% 10% 3 6% 4 4 3 3 4 5% 32%	4560
	11th to 20th	Night	32% 15% 4 10% 5% 5% 3 3 4 5% 15%	5180
	21st to end	Night	31% 15% 4 10% 6% 5% 5% 3 4 4 13%	7050

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	77% 4 6% 9% 3	3477
	11th to 20th	Day	55% 6% 12% 18% 8% 1	3640
	21st to end	Day	60% 4 7% 16% 12%	4073
February	1st to 10th	Day	71% 7% 9% 8% 4 1	1800
	11th to 20th	Day	70% 5% 9% 8% 7% 1	1764
	21st to end	Day	71% 4 10% 11% 4	1569
March	1st to 10th	Day	63% 7% 14% 11% 5%	4579
	11th to 20th	Day	63% 6% 12% 18% 1	5000
	21st to end	Day	71% 8% 13% 8% 1	5700
April	1st to 10th	Day	71% 7% 15% 8% 1	2400
	11th to 20th	Day	65% 6% 12% 11% 5% 1	2258
	21st to end	Day	69% 6% 11% 9% 4 1	2532
May	1st to 10th	Day	53% 5% 16% 18% 9%	4420
	11th to 20th	Day	49% 7% 25% 16% 3	4380
	21st to end	Day	70% 8% 14% 8%	4814
June	1st to 10th	Day	62% 7% 16% 10% 5%	2662
	11th to 20th	Day	67% 6% 14% 10% 2	2850
	21st to end	Day	47% 8% 18% 18% 7% 1	2850
July	1st to 10th	Day	27% 6% 10% 21% 23% 14%	4666
	11th to 20th	Day	23% 4 8% 29% 33% 3	4385
	21st to end	Day	30% 6% 15% 33% 14% 2	4639
August	1st to 10th	Day	23% 6% 13% 39% 16% 1	4341
	11th to 20th	Day	42% 11% 19% 20% 7% 1	4065
	21st to end	Day	45% 4 13% 27% 10% 1	4308
September	1st to 10th	Day	36% 7% 15% 25% 13% 5%	2280
	11th to 20th	Day	48% 6% 12% 17% 14% 2	2280
	21st to end	Day	49% 6% 16% 17% 9% 3	2017
October	1st to 10th	Day	43% 7% 15% 29% 6% 1	3180
	11th to 20th	Day	61% 6% 10% 15% 8% 1	3161
	21st to end	Day	65% 7% 11% 8% 8% 1	3227
November	1st to 10th	Day	70% 5% 11% 10% 4	1630
	11th to 20th	Day	70% 5% 9% 8% 6% 2	1600
	21st to end	Day	69% 5% 6% 10% 7% 2	1600
December	1st to 10th	Day	54% 5% 8% 19% 14% 1	2620
	11th to 20th	Day	74% 6% 9% 9% 1	3028
	21st to end	Day	75% 6% 9% 7% 2	3846
January	1st to 10th	Night	76% 5% 7% 8% 3 1	6422
	11th to 20th	Night	50% 7% 14% 20% 8% 1	6320
	21st to end	Night	59% 4 10% 16% 10% 1	6883
February	1st to 10th	Night	71% 5% 10% 9% 5% 1	2600
	11th to 20th	Night	66% 7% 10% 10% 7% 2	2534
	21st to end	Night	69% 4 10% 12% 4	2060
March	1st to 10th	Night	60% 8% 16% 11% 5%	5300
	11th to 20th	Night	60% 6% 16% 16% 2	5000
	21st to end	Night	72% 8% 13% 7%	5275
April	1st to 10th	Night	68% 8% 12% 10% 1	2000
	11th to 20th	Night	60% 7% 13% 11% 8% 1	1878
	21st to end	Night	66% 7% 11% 11% 5% 1	1648
May	1st to 10th	Night	51% 4 14% 23% 7%	2540
	11th to 20th	Night	50% 6% 21% 19% 3 1	2516
	21st to end	Night	71% 8% 13% 8% 1	2762
June	1st to 10th	Night	60% 5% 16% 14% 5%	1513
	11th to 20th	Night	64% 7% 15% 11% 2	1330
	21st to end	Night	45% 8% 20% 19% 6% 2	1330
July	1st to 10th	Night	30% 6% 10% 18% 17% 19%	2185
	11th to 20th	Night	21% 2 10% 27% 39% 1	2448
	21st to end	Night	31% 6% 14% 28% 19% 2	2674
August	1st to 10th	Night	19% 5% 13% 41% 21% 2	2550
	11th to 20th	Night	40% 10% 18% 21% 8% 2	2839
	21st to end	Night	43% 4 14% 30% 9%	3365
September	1st to 10th	Night	34% 6% 15% 26% 14% 4	1900
	11th to 20th	Night	48% 6% 11% 17% 14% 3	1900
	21st to end	Night	47% 7% 16% 18% 11% 2	2161
October	1st to 10th	Night	44% 6% 14% 30% 6%	3800
	11th to 20th	Night	58% 5% 11% 17% 9% 1	3777
	21st to end	Night	64% 7% 10% 11% 8%	4335
November	1st to 10th	Night	68% 6% 13% 10% 3 1	2666
	11th to 20th	Night	70% 4 10% 10% 4 2	2800
	21st to end	Night	68% 6% 6% 10% 9% 1	2800
December	1st to 10th	Night	55% 5% 8% 17% 13% 1	4560
	11th to 20th	Night	74% 5% 8% 11% 2	5176
	21st to end	Night	75% 7% 9% 6% 2	7050

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	45% 9% 14% 18% 11% 5%	200
	11th to 20th	Day	35% 13% 12% 22% 16% 2	200
	21st to end	Day	48% 7% 14% 14% 14% 4	250
February	1st to 10th	Day	41% 12% 19% 19% 8% 1	400
	11th to 20th	Day	46% 11% 18% 17% 8% 1	395
	21st to end	Day	39% 12% 20% 22% 7% 1	374
March	1st to 10th	Day	37% 14% 19% 20% 9% 1	500
	11th to 20th	Day	33% 14% 17% 23% 10% 3	500
	21st to end	Day	40% 13% 24% 16% 7% 1	550
April	1st to 10th	Day	36% 11% 24% 17% 10% 2	500
	11th to 20th	Day	30% 17% 25% 16% 9% 3	453
	21st to end	Day	32% 12% 26% 21% 9% 1	460
May	1st to 10th	Day	24% 10% 27% 27% 11% 2	463
	11th to 20th	Day	30% 9% 19% 23% 14% 4	488
	21st to end	Day	32% 9% 21% 25% 11% 3	529
June	1st to 10th	Day	28% 9% 22% 27% 12% 3	492
	11th to 20th	Day	30% 12% 23% 24% 10% 1	680
	21st to end	Day	17% 6% 21% 36% 17% 3	680
July	1st to 10th	Day	15% 5% 20% 38% 20% 2	671
	11th to 20th	Day	12% 7% 18% 39% 21% 4	511
	21st to end	Day	11% 4 18% 40% 23% 5%	531
August	1st to 10th	Day	13% 5% 15% 39% 21% 8%	487
	11th to 20th	Day	8% 5% 16% 38% 26% 6%	477
	21st to end	Day	18% 8% 19% 34% 16% 6%	539
September	1st to 10th	Day	15% 9% 22% 35% 16% 3	490
	11th to 20th	Day	21% 8% 17% 33% 19% 2	490
	21st to end	Day	23% 6% 22% 27% 19% 3	490
October	1st to 10th	Day	25% 9% 20% 22% 20% 4	490
	11th to 20th	Day	37% 6% 15% 23% 14% 5%	490
	21st to end	Day	36% 12% 18% 21% 10% 3	406
November	1st to 10th	Day	39% 13% 15% 21% 10% 1	233
	11th to 20th	Day	46% 12% 11% 11% 18% 4	200
	21st to end	Day	39% 9% 13% 20% 13% 8%	200
December	1st to 10th	Day	44% 8% 10% 16% 14% 11%	200
	11th to 20th	Day	44% 13% 16% 20% 8%	200
	21st to end	Day	46% 8% 14% 20% 12% 1	220
January	1st to 10th	Night	49% 8% 14% 17% 11% 1	824
	11th to 20th	Night	40% 9% 15% 23% 12% 2	800
	21st to end	Night	40% 6% 13% 28% 13%	880
February	1st to 10th	Night	41% 7% 17% 25% 9% 1	800
	11th to 20th	Night	39% 8% 12% 29% 11% 1	784
	21st to end	Night	42% 8% 15% 25% 9% 1	660
March	1st to 10th	Night	35% 9% 16% 25% 13% 1	800
	11th to 20th	Night	35% 9% 17% 27% 11% 1	800
	21st to end	Night	41% 8% 16% 25% 8% 2	880
April	1st to 10th	Night	36% 9% 15% 26% 12% 2	800
	11th to 20th	Night	30% 8% 18% 29% 14% 2	748
	21st to end	Night	35% 7% 15% 28% 13% 2	508
May	1st to 10th	Night	26% 8% 13% 33% 19% 1	380
	11th to 20th	Night	28% 5% 10% 28% 25% 4	374
	21st to end	Night	30% 5% 14% 24% 24% 3	411
June	1st to 10th	Night	28% 5% 11% 31% 22% 2	380
	11th to 20th	Night	35% 5% 13% 25% 20% 1	380
	21st to end	Night	19% 3 12% 31% 32% 4	380
July	1st to 10th	Night	16% 5% 8% 30% 36% 4	370
	11th to 20th	Night	13% 2 7% 34% 39% 5%	368
	21st to end	Night	10% 4 7% 27% 46% 6%	416
August	1st to 10th	Night	12% 2 5% 25% 49% 7%	394
	11th to 20th	Night	11% 3 5% 26% 44% 11%	564
	21st to end	Night	20% 3 8% 28% 36% 5%	755
September	1st to 10th	Night	15% 3 8% 36% 33% 5%	760
	11th to 20th	Night	23% 4 9% 26% 32% 6%	760
	21st to end	Night	25% 5% 11% 28% 28% 3	760
October	1st to 10th	Night	27% 5% 11% 31% 24% 3	760
	11th to 20th	Night	33% 6% 13% 26% 18% 3	760
	21st to end	Night	38% 8% 15% 25% 11% 2	836
November	1st to 10th	Night	42% 8% 17% 27% 7%	780
	11th to 20th	Night	45% 7% 16% 23% 9% 1	800
	21st to end	Night	39% 9% 15% 24% 12% 1	800
December	1st to 10th	Night	37% 7% 15% 26% 14% 2	800
	11th to 20th	Night	46% 8% 17% 22% 5% 1	800
	21st to end	Night	50% 9% 16% 20% 5%	902

Page generated at 2025-04-08 06:17:23. Version ac07

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