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 2026-08-15.

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	21% 9% 3 7% 5% 4 4 4 5% 6% 33%	148853
	Night	24% 10% 3 7% 4 4 4 3 4 5% 30%	141623
Transparency	Day	52% 7% 15% 18% 8% 1	148571
	Night	56% 6% 13% 16% 8% 1	141487
Seeing	Day	27% 9% 20% 26% 14% 3	17256
	Night	33% 7% 13% 27% 18% 2	25489

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	37% 17% 4 10% 5% 4 4 3 4 4 8%	4521
	11th to 20th	Day	21% 9% 3 7% 5% 5% 5% 3 5% 6% 31%	4716
	21st to end	Day	30% 10% 3 7% 3 3 3 2 3 4 30%	5283
February	1st to 10th	Day	32% 12% 3 8% 6% 5% 4 4 4 6% 16%	1890
	11th to 20th	Day	31% 14% 4 8% 4 4 4 3 3 4 20%	1845
	21st to end	Day	30% 17% 4 8% 4 4 3 3 4 4 19%	1645
March	1st to 10th	Day	23% 14% 4 9% 6% 5% 5% 4 6% 6% 19%	4680
	11th to 20th	Day	21% 14% 4 9% 5% 5% 5% 3 4 4 26%	5110
	21st to end	Day	27% 13% 4 9% 6% 6% 5% 5% 6% 6% 13%	5826
April	1st to 10th	Day	26% 14% 3 9% 6% 5% 5% 4 5% 6% 17%	2520
	11th to 20th	Day	23% 12% 4 8% 6% 4 5% 4 5% 5% 24%	2496
	21st to end	Day	24% 11% 3 10% 5% 5% 5% 4 5% 6% 22%	2798
May	1st to 10th	Day	14% 7% 2 7% 5% 4 4 4 6% 7% 40%	8195
	11th to 20th	Day	22% 9% 3 8% 5% 5% 5% 4 7% 8% 24%	8160
	21st to end	Day	23% 8% 2 6% 4 4 4 4 6% 9% 30%	8993
June	1st to 10th	Day	24% 9% 2 7% 5% 5% 5% 4 5% 6% 27%	2942
	11th to 20th	Day	26% 10% 3 7% 6% 5% 5% 4 5% 6% 23%	3150
	21st to end	Day	15% 7% 3 8% 5% 4 5% 5% 6% 6% 36%	3150
July	1st to 10th	Day	9% 5% 2 5% 3 3 3 3 5% 6% 56%	8820
	11th to 20th	Day	5% 3 1 4 3 3 3 3 4 6% 65%	8304
	21st to end	Day	9% 4 1 4 3 3 4 3 5% 8% 55%	8916
August	1st to 10th	Day	7% 3 1 3 3 3 3 3 6% 7% 60%	4636
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 7% 8% 38%	4209
	21st to end	Day	17% 8% 3 7% 4 4 4 3 4 7% 41%	4445
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 3 5% 7% 47%	2400
	11th to 20th	Day	17% 7% 3 7% 5% 4 4 4 5% 7% 39%	2400
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 5% 39%	2123
October	1st to 10th	Day	17% 7% 3 5% 3 4 5% 4 6% 9% 37%	3280
	11th to 20th	Day	30% 9% 3 7% 5% 4 3 3 4 7% 25%	3261
	21st to end	Day	29% 10% 3 10% 6% 5% 5% 3 5% 6% 19%	3330
November	1st to 10th	Day	38% 9% 3 7% 4 4 4 5% 4 5% 18%	1713
	11th to 20th	Day	37% 10% 3 7% 4 4 4 3 4 4 20%	1680
	21st to end	Day	35% 11% 3 7% 5% 3 4 3 4 5% 20%	1680
December	1st to 10th	Day	26% 9% 2 6% 4 5% 4 4 6% 5% 30%	2700
	11th to 20th	Day	32% 14% 4 9% 6% 4 4 3 4 4 14%	3105
	21st to end	Day	32% 13% 4 10% 6% 5% 4 3 4 4 14%	3931
January	1st to 10th	Night	35% 16% 4 11% 6% 5% 4 3 4 4 9%	8314
	11th to 20th	Night	21% 9% 4 6% 3 4 4 4 5% 7% 33%	8182
	21st to end	Night	28% 8% 3 7% 4 4 4 3 3 5% 31%	8899
February	1st to 10th	Night	33% 12% 4 8% 5% 4 4 3 4 5% 18%	2730
	11th to 20th	Night	30% 14% 3 7% 4 4 4 3 3 5% 22%	2662
	21st to end	Night	32% 15% 3 7% 4 3 3 4 4 6% 18%	2160
March	1st to 10th	Night	21% 15% 3 8% 5% 5% 5% 5% 6% 7% 20%	5419
	11th to 20th	Night	26% 13% 3 7% 4 4 3 3 4 5% 28%	5109
	21st to end	Night	33% 14% 3 8% 5% 5% 5% 4 5% 4 14%	5391
April	1st to 10th	Night	27% 12% 3 9% 5% 4 5% 5% 5% 6% 19%	2100
	11th to 20th	Night	23% 11% 4 8% 5% 4 4 3 6% 6% 27%	2073
	21st to end	Night	28% 9% 3 7% 5% 5% 3 3 5% 7% 24%	1822
May	1st to 10th	Night	15% 6% 2 7% 5% 4 4 3 4 5% 44%	4724
	11th to 20th	Night	23% 12% 3 9% 6% 5% 4 4 5% 6% 24%	4700
	21st to end	Night	23% 10% 3 8% 5% 4 4 3 5% 6% 27%	5178
June	1st to 10th	Night	22% 8% 3 8% 6% 4 5% 4 5% 5% 31%	1672
	11th to 20th	Night	25% 9% 3 9% 6% 4 4 3 5% 6% 27%	1470
	21st to end	Night	15% 8% 2 7% 5% 4 4 4 5% 6% 41%	1470
July	1st to 10th	Night	13% 6% 2 5% 3 3 3 2 4 5% 54%	4140
	11th to 20th	Night	6% 3 1 3 3 2 3 2 4 5% 68%	4652
	21st to end	Night	10% 5% 2 4 3 3 4 3 4 6% 56%	5152
August	1st to 10th	Night	6% 3 1 3 2 2 3 3 4 6% 67%	2720
	11th to 20th	Night	15% 8% 3 6% 4 3 3 2 4 5% 47%	2938
	21st to end	Night	18% 8% 3 7% 3 2 3 3 3 4 47%	3471
September	1st to 10th	Night	11% 6% 2 5% 3 4 4 3 4 6% 52%	2000
	11th to 20th	Night	19% 8% 3 7% 3 3 4 3 4 5% 41%	2000
	21st to end	Night	19% 7% 2 7% 4 4 4 3 4 5% 40%	2275
October	1st to 10th	Night	18% 7% 2 6% 4 3 4 4 6% 8% 38%	3920
	11th to 20th	Night	29% 8% 2 6% 4 4 4 3 5% 5% 29%	3897
	21st to end	Night	29% 13% 3 9% 5% 4 4 3 4 5% 22%	4474
November	1st to 10th	Night	35% 11% 3 6% 5% 4 4 4 5% 5% 19%	2803
	11th to 20th	Night	36% 11% 3 7% 5% 3 3 2 3 4 21%	2940
	21st to end	Night	33% 12% 3 7% 4 4 4 3 3 5% 21%	2940
December	1st to 10th	Night	25% 10% 3 6% 4 4 3 3 4 5% 32%	4700
	11th to 20th	Night	33% 15% 4 10% 5% 5% 3 3 4 4 14%	5320
	21st to end	Night	30% 15% 4 10% 6% 5% 5% 3 4 4 13%	7206

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	80% 5% 6% 7% 2	4521
	11th to 20th	Day	49% 6% 11% 19% 13% 1	4740
	21st to end	Day	59% 4 6% 17% 14%	5284
February	1st to 10th	Day	71% 7% 9% 9% 4 1	1890
	11th to 20th	Day	70% 5% 9% 9% 7% 1	1854
	21st to end	Day	71% 4 10% 11% 4	1645
March	1st to 10th	Day	63% 7% 14% 11% 5%	4680
	11th to 20th	Day	63% 6% 12% 17% 1	5110
	21st to end	Day	71% 8% 13% 8% 1	5826
April	1st to 10th	Day	69% 7% 15% 8% 1	2520
	11th to 20th	Day	63% 7% 12% 13% 5% 1	2496
	21st to end	Day	66% 6% 12% 11% 4 1	2798
May	1st to 10th	Day	44% 6% 20% 23% 7%	8195
	11th to 20th	Day	57% 10% 20% 12% 2	8163
	21st to end	Day	52% 10% 24% 13% 1	8994
June	1st to 10th	Day	59% 7% 17% 12% 5%	2942
	11th to 20th	Day	63% 6% 14% 13% 3	3150
	21st to end	Day	48% 8% 18% 18% 7% 1	3150
July	1st to 10th	Day	28% 8% 18% 21% 18% 7%	8746
	11th to 20th	Day	21% 5% 14% 29% 29% 2	8227
	21st to end	Day	27% 8% 21% 32% 11% 1	8723
August	1st to 10th	Day	24% 7% 13% 38% 17% 2	4619
	11th to 20th	Day	42% 11% 18% 20% 7% 1	4248
	21st to end	Day	45% 4 13% 27% 11% 1	4444
September	1st to 10th	Day	37% 7% 15% 24% 12% 5%	2400
	11th to 20th	Day	47% 7% 12% 18% 14% 2	2400
	21st to end	Day	48% 6% 17% 18% 9% 2	2123
October	1st to 10th	Day	43% 7% 15% 29% 6%	3280
	11th to 20th	Day	61% 6% 10% 15% 8%	3261
	21st to end	Day	65% 8% 11% 8% 7% 1	3330
November	1st to 10th	Day	69% 6% 12% 10% 3	1713
	11th to 20th	Day	70% 5% 9% 8% 6% 2	1680
	21st to end	Day	69% 5% 6% 10% 7% 2	1680
December	1st to 10th	Day	56% 5% 7% 18% 13% 1	2700
	11th to 20th	Day	74% 6% 9% 9% 2	3108
	21st to end	Day	75% 6% 9% 8% 2	3931
January	1st to 10th	Night	78% 5% 6% 8% 3	8314
	11th to 20th	Night	46% 6% 13% 21% 13% 1	8220
	21st to end	Night	58% 4 9% 17% 12% 1	8899
February	1st to 10th	Night	70% 5% 10% 9% 5% 1	2730
	11th to 20th	Night	65% 7% 9% 10% 7% 1	2664
	21st to end	Night	70% 5% 10% 11% 4	2160
March	1st to 10th	Night	60% 8% 16% 11% 5%	5419
	11th to 20th	Night	60% 5% 16% 16% 2	5110
	21st to end	Night	71% 8% 13% 7% 1	5391
April	1st to 10th	Night	67% 8% 13% 11% 1	2100
	11th to 20th	Night	59% 7% 14% 11% 8% 1	2073
	21st to end	Night	63% 7% 12% 12% 5% 1	1822
May	1st to 10th	Night	43% 6% 17% 28% 6%	4721
	11th to 20th	Night	61% 8% 16% 13% 2	4700
	21st to end	Night	57% 9% 21% 11% 2	5182
June	1st to 10th	Night	58% 5% 17% 15% 5%	1672
	11th to 20th	Night	60% 7% 15% 15% 3	1470
	21st to end	Night	46% 8% 19% 20% 6% 2	1470
July	1st to 10th	Night	34% 6% 17% 19% 13% 10%	4105
	11th to 20th	Night	20% 5% 13% 27% 34% 1	4606
	21st to end	Night	28% 6% 21% 31% 12% 1	5040
August	1st to 10th	Night	20% 5% 13% 41% 20% 2	2712
	11th to 20th	Night	40% 10% 18% 21% 9% 2	2965
	21st to end	Night	43% 4 14% 30% 9% 1	3471
September	1st to 10th	Night	34% 6% 16% 26% 13% 4	2000
	11th to 20th	Night	47% 7% 12% 18% 14% 3	2000
	21st to end	Night	47% 7% 15% 18% 10% 2	2275
October	1st to 10th	Night	44% 7% 15% 29% 5%	3920
	11th to 20th	Night	58% 5% 10% 17% 9%	3897
	21st to end	Night	64% 7% 10% 11% 8%	4474
November	1st to 10th	Night	68% 6% 13% 10% 3	2803
	11th to 20th	Night	70% 4 9% 10% 4 2	2940
	21st to end	Night	69% 5% 7% 10% 8% 1	2940
December	1st to 10th	Night	56% 5% 8% 17% 13% 1	4700
	11th to 20th	Night	74% 5% 8% 10% 2	5316
	21st to end	Night	75% 7% 10% 6% 2	7206

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	43% 11% 15% 17% 10% 4	220
	11th to 20th	Day	34% 12% 11% 21% 19% 4	220
	21st to end	Day	46% 7% 14% 16% 14% 3	274
February	1st to 10th	Day	40% 12% 18% 19% 10% 1	430
	11th to 20th	Day	44% 11% 20% 18% 8%	425
	21st to end	Day	40% 12% 20% 21% 7% 1	402
March	1st to 10th	Day	39% 14% 19% 19% 9% 1	540
	11th to 20th	Day	36% 13% 17% 22% 9% 3	540
	21st to end	Day	39% 12% 25% 16% 7% 1	594
April	1st to 10th	Day	34% 11% 23% 19% 10% 3	540
	11th to 20th	Day	29% 16% 25% 18% 10% 2	532
	21st to end	Day	29% 12% 25% 22% 10% 2	540
May	1st to 10th	Day	22% 10% 27% 27% 11% 2	543
	11th to 20th	Day	31% 10% 20% 23% 13% 4	568
	21st to end	Day	29% 9% 22% 26% 12% 3	617
June	1st to 10th	Day	26% 10% 21% 27% 13% 3	572
	11th to 20th	Day	27% 11% 24% 26% 11% 2	780
	21st to end	Day	17% 7% 20% 36% 17% 3	780
July	1st to 10th	Day	14% 6% 20% 39% 20% 2	771
	11th to 20th	Day	10% 7% 22% 37% 20% 4	594
	21st to end	Day	10% 5% 19% 40% 22% 5%	619
August	1st to 10th	Day	13% 6% 16% 37% 20% 8%	567
	11th to 20th	Day	9% 5% 17% 37% 26% 7%	534
	21st to end	Day	16% 9% 19% 35% 15% 7%	583
September	1st to 10th	Day	15% 9% 21% 35% 17% 4	530
	11th to 20th	Day	21% 8% 18% 32% 19% 2	530
	21st to end	Day	23% 6% 22% 28% 18% 3	530
October	1st to 10th	Day	24% 8% 22% 22% 19% 4	530
	11th to 20th	Day	36% 6% 16% 23% 14% 4	530
	21st to end	Day	35% 12% 19% 21% 9% 3	443
November	1st to 10th	Day	39% 14% 16% 20% 11% 1	256
	11th to 20th	Day	46% 11% 11% 11% 17% 4	220
	21st to end	Day	38% 10% 14% 20% 12% 7%	220
December	1st to 10th	Day	45% 8% 10% 15% 12% 10%	220
	11th to 20th	Day	48% 12% 15% 18% 8%	220
	21st to end	Day	44% 7% 14% 21% 12% 2	242
January	1st to 10th	Night	48% 9% 14% 17% 11% 1	866
	11th to 20th	Night	39% 8% 14% 24% 13% 2	840
	21st to end	Night	39% 6% 13% 28% 13%	924
February	1st to 10th	Night	41% 8% 18% 25% 9% 1	840
	11th to 20th	Night	38% 8% 12% 29% 12% 1	824
	21st to end	Night	41% 9% 15% 25% 8% 1	692
March	1st to 10th	Night	36% 9% 16% 25% 13% 1	840
	11th to 20th	Night	38% 9% 16% 26% 10% 1	840
	21st to end	Night	40% 8% 17% 25% 8% 2	924
April	1st to 10th	Night	34% 9% 14% 27% 13% 2	840
	11th to 20th	Night	29% 8% 17% 30% 14% 1	825
	21st to end	Night	34% 8% 15% 28% 14% 2	562
May	1st to 10th	Night	24% 9% 12% 35% 20%	420
	11th to 20th	Night	28% 7% 11% 27% 22% 4	414
	21st to end	Night	28% 5% 14% 25% 23% 3	455
June	1st to 10th	Night	28% 5% 11% 31% 23% 2	420
	11th to 20th	Night	32% 5% 13% 29% 20% 1	420
	21st to end	Night	20% 4 12% 30% 31% 4	420
July	1st to 10th	Night	16% 5% 8% 31% 35% 4	410
	11th to 20th	Night	12% 2 7% 37% 38% 4	408
	21st to end	Night	10% 4 7% 27% 47% 5%	460
August	1st to 10th	Night	12% 2 6% 25% 48% 6%	436
	11th to 20th	Night	12% 3 5% 25% 44% 11%	606
	21st to end	Night	19% 4 7% 28% 37% 5%	795
September	1st to 10th	Night	15% 4 8% 35% 34% 6%	800
	11th to 20th	Night	23% 4 9% 27% 32% 6%	800
	21st to end	Night	25% 5% 11% 29% 28% 3	800
October	1st to 10th	Night	26% 5% 12% 31% 24% 3	800
	11th to 20th	Night	34% 6% 13% 27% 17% 3	800
	21st to end	Night	37% 9% 16% 25% 11% 2	880
November	1st to 10th	Night	42% 9% 17% 26% 6%	820
	11th to 20th	Night	45% 8% 16% 23% 8% 1	840
	21st to end	Night	39% 9% 15% 24% 12% 1	840
December	1st to 10th	Night	38% 7% 15% 25% 13% 2	840
	11th to 20th	Night	48% 8% 17% 22% 5% 1	840
	21st to end	Night	49% 9% 16% 20% 6%	948

Page generated at 2026-08-12 00:37:14. Version ac07

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