Caroline
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caroline 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	8% 9% 3 8% 5% 5% 5% 5% 7% 8% 35%	148702
	Night	6% 9% 4 9% 6% 5% 5% 4 6% 8% 35%	141890
Transparency	Day	42% 8% 16% 23% 10% 1	148405
	Night	43% 7% 15% 22% 10% 2	141771
Seeing	Day	13% 8% 26% 31% 17% 5%	17682
	Night	12% 6% 30% 36% 15% 2	26568

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	3 11% 5% 13% 7% 6% 6% 4 7% 8% 30%	4125
	11th to 20th	Day	2 7% 3 10% 6% 5% 7% 5% 6% 8% 41%	4161
	21st to end	Day	2 9% 4 9% 5% 5% 6% 4 7% 9% 39%	5186
February	1st to 10th	Day	4 13% 4 11% 9% 6% 7% 5% 6% 7% 29%	1680
	11th to 20th	Day	4 13% 4 13% 6% 6% 6% 4 7% 8% 29%	1774
	21st to end	Day	3 9% 5% 12% 9% 7% 7% 5% 8% 7% 29%	1699
March	1st to 10th	Day	2 8% 4 12% 6% 5% 6% 4 6% 9% 38%	4618
	11th to 20th	Day	5% 10% 5% 10% 5% 4 5% 5% 7% 9% 36%	4974
	21st to end	Day	8% 20% 7% 12% 6% 5% 5% 4 5% 6% 22%	5785
April	1st to 10th	Day	7% 15% 5% 9% 7% 6% 7% 5% 7% 8% 25%	2562
	11th to 20th	Day	11% 16% 4 9% 5% 5% 5% 5% 6% 7% 26%	2700
	21st to end	Day	11% 12% 4 9% 6% 5% 5% 5% 6% 9% 29%	2730
May	1st to 10th	Day	10% 10% 3 8% 6% 5% 5% 5% 6% 7% 35%	8283
	11th to 20th	Day	12% 11% 4 10% 7% 7% 6% 5% 6% 9% 23%	8755
	21st to end	Day	13% 9% 3 8% 6% 5% 5% 4 7% 8% 30%	9649
June	1st to 10th	Day	18% 8% 3 7% 7% 6% 5% 5% 7% 7% 27%	3150
	11th to 20th	Day	19% 10% 3 8% 6% 6% 7% 5% 6% 7% 23%	3150
	21st to end	Day	11% 7% 3 7% 6% 7% 6% 6% 7% 9% 32%	3150
July	1st to 10th	Day	6% 5% 2 5% 4 5% 5% 6% 8% 10% 43%	8820
	11th to 20th	Day	10% 5% 2 5% 4 4 6% 5% 8% 10% 41%	8820
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 8% 9% 46%	9392
August	1st to 10th	Day	11% 5% 2 6% 4 4 5% 5% 7% 9% 41%	4681
	11th to 20th	Day	9% 5% 2 6% 5% 5% 6% 5% 9% 11% 38%	4350
	21st to end	Day	10% 5% 2 6% 4 4 4 5% 7% 9% 45%	4664
September	1st to 10th	Day	12% 6% 2 6% 3 4 4 4 6% 8% 45%	2472
	11th to 20th	Day	15% 8% 3 6% 4 4 3 3 5% 6% 44%	2220
	21st to end	Day	10% 8% 3 7% 4 5% 4 3 6% 8% 42%	2200
October	1st to 10th	Day	7% 7% 3 7% 5% 4 6% 5% 6% 9% 42%	3467
	11th to 20th	Day	8% 7% 3 8% 6% 5% 6% 5% 8% 9% 36%	2932
	21st to end	Day	6% 8% 3 9% 5% 5% 5% 4 5% 7% 41%	3200
November	1st to 10th	Day	6% 15% 6% 8% 7% 6% 4 5% 6% 7% 31%	1719
	11th to 20th	Day	5% 12% 4 10% 5% 6% 4 3 7% 7% 36%	1517
	21st to end	Day	5% 13% 3 10% 6% 5% 5% 5% 7% 8% 33%	1470
December	1st to 10th	Day	5% 10% 4 13% 7% 8% 7% 6% 6% 9% 26%	2360
	11th to 20th	Day	3 11% 4 12% 7% 6% 6% 6% 7% 7% 31%	2712
	21st to end	Day	3 10% 5% 10% 6% 5% 5% 4 6% 7% 38%	3575
January	1st to 10th	Night	3 12% 7% 14% 8% 8% 6% 5% 6% 7% 24%	8768
	11th to 20th	Night	1 7% 4 12% 8% 6% 6% 5% 6% 7% 38%	8779
	21st to end	Night	2 9% 4 10% 6% 6% 6% 5% 7% 9% 36%	8995
February	1st to 10th	Night	5% 11% 5% 13% 8% 6% 7% 5% 6% 8% 27%	2940
	11th to 20th	Night	4 11% 4 13% 8% 8% 6% 4 7% 8% 28%	2733
	21st to end	Night	2 10% 5% 13% 7% 6% 5% 4 5% 7% 35%	2107
March	1st to 10th	Night	2 9% 4 11% 7% 5% 5% 5% 6% 8% 37%	5496
	11th to 20th	Night	5% 10% 4 10% 6% 5% 5% 5% 8% 10% 31%	5245
	21st to end	Night	8% 17% 5% 12% 6% 5% 5% 4 5% 7% 25%	5431
April	1st to 10th	Night	8% 11% 4 9% 7% 6% 5% 4 6% 9% 31%	2058
	11th to 20th	Night	9% 15% 5% 11% 7% 4 4 3 6% 7% 29%	1871
	21st to end	Night	10% 11% 4 10% 6% 5% 5% 4 6% 8% 31%	1890
May	1st to 10th	Night	15% 12% 3 8% 5% 4 4 3 4 6% 36%	4635
	11th to 20th	Night	12% 10% 4 9% 5% 5% 5% 4 8% 9% 28%	4105
	21st to end	Night	10% 7% 3 8% 6% 5% 6% 5% 7% 8% 35%	4522
June	1st to 10th	Night	17% 9% 3 6% 6% 5% 6% 5% 6% 8% 30%	1470
	11th to 20th	Night	16% 10% 3 10% 6% 6% 6% 4 8% 7% 26%	1470
	21st to end	Night	11% 6% 2 7% 5% 6% 6% 5% 8% 8% 37%	1470
July	1st to 10th	Night	7% 5% 2 7% 5% 5% 6% 4 7% 9% 42%	4140
	11th to 20th	Night	8% 5% 1 5% 3 4 4 4 7% 9% 50%	4140
	21st to end	Night	8% 6% 2 5% 4 4 4 3 6% 9% 50%	4673
August	1st to 10th	Night	13% 5% 2 6% 4 4 4 4 6% 7% 44%	2689
	11th to 20th	Night	11% 6% 3 6% 4 3 5% 5% 8% 11% 38%	2792
	21st to end	Night	11% 6% 3 6% 4 3 4 4 5% 7% 48%	3245
September	1st to 10th	Night	11% 7% 2 6% 4 3 4 3 5% 8% 47%	1925
	11th to 20th	Night	14% 7% 2 7% 4 3 4 4 6% 7% 41%	2180
	21st to end	Night	10% 7% 3 6% 3 5% 5% 4 7% 8% 44%	2200
October	1st to 10th	Night	6% 7% 2 7% 5% 5% 5% 4 7% 8% 44%	3713
	11th to 20th	Night	7% 9% 3 8% 4 5% 5% 4 6% 9% 41%	4216
	21st to end	Night	6% 9% 3 8% 5% 5% 5% 4 6% 8% 41%	4600
November	1st to 10th	Night	8% 14% 4 10% 5% 5% 5% 5% 6% 7% 32%	2777
	11th to 20th	Night	5% 11% 4 10% 6% 6% 6% 4 7% 8% 32%	3102
	21st to end	Night	4 12% 4 10% 7% 6% 6% 5% 7% 8% 33%	3150
December	1st to 10th	Night	6% 12% 4 11% 7% 6% 7% 5% 6% 8% 28%	5040
	11th to 20th	Night	3 13% 5% 13% 9% 7% 7% 5% 6% 8% 25%	5700
	21st to end	Night	3 10% 4 10% 6% 5% 5% 4 6% 8% 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	50% 5% 10% 19% 13% 2	4125
	11th to 20th	Day	39% 6% 14% 19% 18% 3	4182
	21st to end	Day	37% 8% 14% 30% 11%	5187
February	1st to 10th	Day	51% 7% 13% 16% 11% 3	1680
	11th to 20th	Day	49% 9% 14% 17% 10% 2	1782
	21st to end	Day	49% 8% 12% 18% 11% 1	1699
March	1st to 10th	Day	40% 7% 15% 22% 15%	4618
	11th to 20th	Day	40% 7% 15% 23% 13% 1	4975
	21st to end	Day	60% 8% 11% 14% 6% 1	5785
April	1st to 10th	Day	52% 10% 16% 15% 6%	2562
	11th to 20th	Day	53% 7% 13% 18% 8%	2700
	21st to end	Day	50% 9% 14% 19% 6% 1	2730
May	1st to 10th	Day	44% 6% 11% 26% 12% 1	8283
	11th to 20th	Day	52% 8% 13% 20% 6% 1	8759
	21st to end	Day	47% 9% 17% 20% 7%	9650
June	1st to 10th	Day	52% 9% 15% 16% 7% 1	3150
	11th to 20th	Day	56% 9% 15% 14% 5% 1	3150
	21st to end	Day	43% 11% 19% 21% 6% 1	3150
July	1st to 10th	Day	31% 8% 19% 27% 12% 2	8746
	11th to 20th	Day	35% 8% 20% 26% 9% 3	8739
	21st to end	Day	31% 8% 21% 26% 13% 2	9188
August	1st to 10th	Day	37% 9% 19% 28% 7%	4664
	11th to 20th	Day	35% 10% 23% 25% 8% 1	4392
	21st to end	Day	33% 8% 21% 30% 8% 1	4663
September	1st to 10th	Day	35% 7% 21% 23% 11% 2	2472
	11th to 20th	Day	40% 7% 14% 28% 10% 1	2220
	21st to end	Day	38% 9% 16% 24% 11% 3	2200
October	1st to 10th	Day	36% 6% 20% 30% 6% 1	3467
	11th to 20th	Day	41% 7% 17% 20% 13% 3	2932
	21st to end	Day	40% 6% 10% 32% 11% 1	3200
November	1st to 10th	Day	51% 8% 13% 18% 9% 2	1719
	11th to 20th	Day	45% 8% 14% 22% 11% 1	1517
	21st to end	Day	46% 8% 17% 18% 8% 3	1470
December	1st to 10th	Day	54% 6% 14% 18% 7% 1	2360
	11th to 20th	Day	47% 8% 19% 18% 6% 1	2714
	21st to end	Day	41% 7% 10% 21% 18% 3	3575
January	1st to 10th	Night	56% 7% 11% 16% 8% 2	8769
	11th to 20th	Night	42% 6% 15% 20% 13% 5%	8820
	21st to end	Night	41% 8% 18% 24% 10% 1	8995
February	1st to 10th	Night	52% 8% 11% 16% 11% 2	2940
	11th to 20th	Night	51% 7% 13% 16% 12% 1	2735
	21st to end	Night	45% 5% 12% 22% 13% 2	2107
March	1st to 10th	Night	41% 9% 16% 21% 12% 1	5496
	11th to 20th	Night	42% 9% 15% 19% 14% 1	5245
	21st to end	Night	57% 8% 10% 15% 10% 1	5431
April	1st to 10th	Night	47% 8% 15% 20% 10% 1	2058
	11th to 20th	Night	51% 7% 14% 17% 9% 1	1871
	21st to end	Night	48% 8% 15% 21% 7% 1	1890
May	1st to 10th	Night	48% 5% 10% 22% 12% 2	4632
	11th to 20th	Night	46% 9% 15% 22% 9%	4105
	21st to end	Night	41% 11% 17% 25% 6% 1	4526
June	1st to 10th	Night	49% 10% 13% 18% 10% 1	1470
	11th to 20th	Night	53% 9% 14% 18% 5% 1	1470
	21st to end	Night	40% 11% 19% 24% 6% 1	1470
July	1st to 10th	Night	34% 9% 18% 28% 9% 2	4105
	11th to 20th	Night	28% 6% 23% 28% 11% 4	4098
	21st to end	Night	31% 6% 23% 26% 12% 2	4573
August	1st to 10th	Night	38% 9% 17% 29% 7%	2681
	11th to 20th	Night	35% 10% 24% 24% 6% 1	2816
	21st to end	Night	35% 6% 18% 31% 9% 1	3245
September	1st to 10th	Night	34% 7% 19% 24% 13% 3	1925
	11th to 20th	Night	39% 7% 14% 25% 11% 3	2180
	21st to end	Night	36% 7% 17% 24% 13% 3	2200
October	1st to 10th	Night	35% 6% 18% 27% 12% 1	3713
	11th to 20th	Night	38% 6% 16% 28% 11% 2	4216
	21st to end	Night	39% 6% 13% 29% 12%	4600
November	1st to 10th	Night	49% 7% 12% 20% 11% 2	2777
	11th to 20th	Night	46% 8% 16% 18% 11% 1	3102
	21st to end	Night	45% 8% 15% 20% 8% 3	3150
December	1st to 10th	Night	53% 6% 15% 18% 7% 2	5040
	11th to 20th	Night	55% 9% 14% 16% 6% 1	5697
	21st to end	Night	40% 6% 11% 23% 17% 4	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	5% 5% 31% 32% 17% 10%	220
	11th to 20th	Day	5% 5% 37% 35% 15% 4	220
	21st to end	Day	8% 8% 28% 31% 19% 6%	242
February	1st to 10th	Day	9% 10% 26% 37% 12% 6%	220
	11th to 20th	Day	10% 5% 32% 33% 17% 2	292
	21st to end	Day	4 9% 30% 37% 17% 3	415
March	1st to 10th	Day	8% 10% 34% 31% 14% 4	540
	11th to 20th	Day	8% 8% 33% 32% 14% 5%	540
	21st to end	Day	16% 10% 32% 26% 13% 4	594
April	1st to 10th	Day	13% 12% 32% 26% 14% 3	540
	11th to 20th	Day	16% 11% 28% 27% 14% 5%	532
	21st to end	Day	15% 13% 24% 28% 15% 4	540
May	1st to 10th	Day	17% 12% 23% 27% 16% 4	594
	11th to 20th	Day	15% 7% 23% 32% 18% 4	775
	21st to end	Day	18% 6% 19% 30% 20% 6%	844
June	1st to 10th	Day	18% 9% 24% 34% 12% 3	780
	11th to 20th	Day	21% 7% 25% 28% 15% 5%	780
	21st to end	Day	13% 5% 22% 31% 22% 8%	780
July	1st to 10th	Day	13% 4 21% 32% 23% 7%	771
	11th to 20th	Day	15% 6% 20% 32% 23% 5%	768
	21st to end	Day	9% 5% 23% 32% 25% 7%	786
August	1st to 10th	Day	11% 5% 24% 34% 18% 8%	567
	11th to 20th	Day	10% 5% 24% 33% 24% 5%	534
	21st to end	Day	10% 6% 22% 30% 22% 9%	583
September	1st to 10th	Day	14% 7% 26% 30% 16% 8%	530
	11th to 20th	Day	18% 6% 21% 28% 20% 8%	530
	21st to end	Day	13% 11% 32% 28% 12% 4	530
October	1st to 10th	Day	14% 8% 23% 30% 17% 7%	465
	11th to 20th	Day	14% 7% 31% 29% 15% 5%	330
	21st to end	Day	12% 14% 31% 28% 11% 3	363
November	1st to 10th	Day	15% 5% 26% 37% 13% 3	330
	11th to 20th	Day	13% 9% 33% 30% 12% 2	245
	21st to end	Day	6% 7% 28% 37% 15% 6%	220
December	1st to 10th	Day	7% 5% 32% 36% 17% 4	220
	11th to 20th	Day	7% 11% 35% 30% 11% 5%	220
	21st to end	Day	7% 6% 25% 32% 23% 7%	242
January	1st to 10th	Night	10% 8% 34% 34% 13% 1	1050
	11th to 20th	Night	7% 9% 36% 35% 12% 1	1050
	21st to end	Night	10% 10% 35% 33% 11% 2	925
February	1st to 10th	Night	10% 8% 29% 35% 15% 3	840
	11th to 20th	Night	7% 8% 32% 37% 15% 1	824
	21st to end	Night	7% 5% 31% 35% 18% 5%	692
March	1st to 10th	Night	8% 5% 32% 38% 14% 3	840
	11th to 20th	Night	8% 5% 35% 38% 12% 2	840
	21st to end	Night	13% 6% 29% 36% 13% 2	924
April	1st to 10th	Night	11% 8% 31% 35% 14% 1	798
	11th to 20th	Night	16% 6% 35% 33% 9% 1	623
	21st to end	Night	16% 12% 24% 36% 12% 1	630
May	1st to 10th	Night	19% 7% 24% 37% 11% 2	446
	11th to 20th	Night	14% 5% 24% 40% 16% 1	414
	21st to end	Night	21% 5% 21% 34% 19% 1	455
June	1st to 10th	Night	19% 5% 24% 38% 13% 1	420
	11th to 20th	Night	18% 5% 24% 35% 16% 1	420
	21st to end	Night	14% 3 19% 37% 25% 2	420
July	1st to 10th	Night	15% 2 17% 43% 22% 1	410
	11th to 20th	Night	13% 4 20% 43% 19% 1	408
	21st to end	Night	8% 4 17% 44% 25% 2	460
August	1st to 10th	Night	12% 4 16% 36% 28% 4	418
	11th to 20th	Night	13% 5% 15% 40% 27% 2	509
	21st to end	Night	12% 3 19% 42% 22%	660
September	1st to 10th	Night	14% 2 19% 40% 22% 2	725
	11th to 20th	Night	17% 3 20% 34% 22% 3	800
	21st to end	Night	13% 5% 30% 37% 14% 2	800
October	1st to 10th	Night	14% 5% 27% 36% 15% 2	800
	11th to 20th	Night	12% 5% 31% 36% 14% 2	800
	21st to end	Night	12% 7% 34% 35% 11% 1	880
November	1st to 10th	Night	15% 7% 34% 30% 12% 2	932
	11th to 20th	Night	10% 8% 40% 32% 9% 1	1050
	21st to end	Night	9% 5% 38% 35% 10% 3	1050
December	1st to 10th	Night	12% 8% 34% 34% 11% 2	1050
	11th to 20th	Night	9% 6% 36% 36% 12% 1	1050
	21st to end	Night	10% 5% 33% 36% 13% 3	1155

Page generated at 2026-08-12 01:37:17. Version ac07

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