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 2024-10-24.

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% 10% 3 8% 5% 5% 5% 5% 7% 8% 34%	101874
	Night	7% 10% 4 9% 6% 5% 5% 4 6% 8% 35%	96963
Transparency	Day	43% 9% 16% 21% 9% 1	101621
	Night	44% 9% 15% 21% 10% 2	96863
Seeing	Day	13% 8% 26% 31% 17% 5%	15322
	Night	12% 6% 29% 36% 15% 2	24262

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 12% 6% 14% 6% 4 3 4 6% 9% 32%	2219
	11th to 20th	Day	3 10% 4 10% 6% 5% 7% 5% 7% 8% 35%	2213
	21st to end	Day	4 10% 3 8% 5% 5% 6% 4 7% 10% 38%	2794
February	1st to 10th	Day	4 14% 5% 10% 8% 6% 6% 5% 6% 7% 28%	1520
	11th to 20th	Day	4 14% 4 13% 6% 6% 6% 5% 7% 8% 27%	1600
	21st to end	Day	3 9% 5% 13% 9% 7% 6% 5% 8% 6% 28%	1541
March	1st to 10th	Day	2 10% 5% 14% 7% 6% 7% 4 7% 7% 32%	3138
	11th to 20th	Day	6% 10% 3 7% 4 4 5% 5% 8% 9% 40%	3396
	21st to end	Day	6% 20% 7% 12% 6% 5% 4 4 5% 6% 25%	3947
April	1st to 10th	Day	7% 15% 4 9% 7% 6% 6% 5% 7% 8% 25%	2318
	11th to 20th	Day	11% 16% 4 10% 5% 5% 5% 5% 6% 7% 26%	2440
	21st to end	Day	11% 12% 4 9% 6% 5% 5% 5% 6% 9% 28%	2470
May	1st to 10th	Day	16% 14% 3 9% 5% 5% 5% 4 5% 6% 27%	4466
	11th to 20th	Day	11% 11% 4 10% 6% 6% 6% 5% 6% 9% 27%	4694
	21st to end	Day	17% 11% 4 10% 7% 6% 5% 5% 7% 7% 21%	5161
June	1st to 10th	Day	18% 8% 3 7% 7% 6% 5% 5% 8% 7% 26%	2850
	11th to 20th	Day	20% 10% 3 8% 6% 6% 6% 5% 6% 7% 23%	2850
	21st to end	Day	11% 7% 2 6% 6% 6% 6% 6% 7% 9% 33%	2850
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 8% 44%	4740
	11th to 20th	Day	8% 4 2 4 4 4 6% 6% 8% 10% 44%	4740
	21st to end	Day	7% 5% 2 5% 5% 4 5% 5% 8% 9% 45%	5045
August	1st to 10th	Day	11% 5% 2 6% 4 4 5% 5% 7% 9% 41%	4401
	11th to 20th	Day	8% 5% 2 6% 4 5% 6% 5% 8% 11% 39%	4159
	21st to end	Day	10% 5% 2 6% 4 5% 5% 5% 7% 9% 43%	4521
September	1st to 10th	Day	13% 6% 2 6% 3 4 5% 4 6% 8% 44%	2349
	11th to 20th	Day	15% 9% 3 6% 4 4 3 3 5% 6% 43%	2109
	21st to end	Day	10% 8% 3 7% 4 5% 4 4 6% 8% 41%	2090
October	1st to 10th	Day	11% 9% 3 6% 4 4 4 5% 6% 7% 39%	2024
	11th to 20th	Day	10% 9% 3 8% 5% 4 5% 4 6% 7% 38%	1710
	21st to end	Day	8% 10% 4 9% 6% 5% 5% 5% 6% 8% 34%	1809
November	1st to 10th	Day	6% 16% 6% 8% 7% 6% 4 4 6% 6% 31%	1553
	11th to 20th	Day	6% 12% 4 10% 5% 6% 4 3 7% 7% 36%	1373
	21st to end	Day	5% 13% 3 9% 6% 5% 5% 4 7% 9% 35%	1330
December	1st to 10th	Day	5% 11% 4 13% 8% 6% 5% 5% 5% 8% 28%	1330
	11th to 20th	Day	3 10% 5% 14% 7% 6% 6% 6% 7% 7% 31%	1682
	21st to end	Day	3 9% 4 10% 7% 5% 4 4 7% 7% 40%	2442
January	1st to 10th	Night	3 12% 7% 14% 7% 7% 6% 4 6% 7% 27%	4726
	11th to 20th	Night	2 9% 5% 13% 8% 5% 5% 6% 7% 7% 33%	4699
	21st to end	Night	3 10% 4 10% 7% 6% 5% 5% 7% 10% 32%	4863
February	1st to 10th	Night	5% 11% 5% 14% 8% 5% 6% 5% 5% 8% 28%	2660
	11th to 20th	Night	4 12% 5% 13% 7% 7% 6% 4 7% 7% 28%	2467
	21st to end	Night	2 10% 5% 13% 7% 6% 5% 4 5% 7% 36%	1913
March	1st to 10th	Night	2 9% 4 14% 9% 6% 6% 6% 7% 8% 28%	3736
	11th to 20th	Night	6% 10% 3 6% 5% 5% 5% 5% 8% 9% 38%	3583
	21st to end	Night	7% 18% 6% 13% 7% 6% 5% 4 5% 7% 23%	3705
April	1st to 10th	Night	8% 11% 3 10% 7% 6% 5% 5% 7% 9% 29%	1862
	11th to 20th	Night	9% 15% 5% 11% 7% 4 4 3 6% 7% 29%	1691
	21st to end	Night	11% 11% 4 9% 6% 5% 5% 4 6% 8% 31%	1710
May	1st to 10th	Night	21% 14% 4 8% 5% 4 4 3 3 5% 28%	2491
	11th to 20th	Night	11% 8% 3 8% 5% 4 5% 5% 9% 10% 31%	2199
	21st to end	Night	16% 10% 4 9% 7% 5% 6% 6% 7% 7% 23%	2414
June	1st to 10th	Night	17% 9% 3 7% 5% 4 6% 5% 6% 8% 30%	1330
	11th to 20th	Night	16% 10% 3 9% 6% 6% 6% 5% 7% 6% 26%	1330
	21st to end	Night	9% 6% 2 7% 5% 5% 6% 5% 8% 9% 38%	1330
July	1st to 10th	Night	9% 6% 2 8% 5% 6% 6% 4 6% 8% 40%	2220
	11th to 20th	Night	7% 4 1 5% 3 3 4 5% 8% 10% 50%	2220
	21st to end	Night	6% 7% 2 6% 4 4 4 4 6% 9% 48%	2504
August	1st to 10th	Night	13% 5% 2 6% 4 4 4 4 6% 7% 44%	2529
	11th to 20th	Night	10% 6% 3 6% 4 3 5% 5% 8% 11% 39%	2675
	21st to end	Night	11% 6% 3 6% 4 3 5% 4 5% 7% 47%	3146
September	1st to 10th	Night	11% 7% 2 6% 4 3 4 3 5% 7% 47%	1829
	11th to 20th	Night	14% 8% 3 7% 4 3 4 4 6% 7% 40%	2071
	21st to end	Night	10% 7% 2 6% 3 5% 5% 4 7% 8% 44%	2090
October	1st to 10th	Night	9% 9% 3 8% 5% 4 4 4 6% 6% 42%	2152
	11th to 20th	Night	8% 9% 3 9% 4 5% 5% 4 6% 9% 37%	2470
	21st to end	Night	8% 10% 3 9% 6% 5% 6% 4 7% 8% 34%	2613
November	1st to 10th	Night	8% 15% 4 10% 5% 5% 5% 5% 6% 7% 32%	2505
	11th to 20th	Night	5% 11% 4 10% 6% 6% 6% 4 7% 8% 33%	2806
	21st to end	Night	4 12% 4 10% 7% 5% 6% 4 7% 9% 32%	2850
December	1st to 10th	Night	6% 12% 4 10% 7% 5% 5% 4 6% 7% 34%	2850
	11th to 20th	Night	3 10% 4 11% 8% 6% 7% 5% 7% 8% 29%	3510
	21st to end	Night	3 10% 3 9% 5% 5% 5% 4 6% 7% 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	46% 6% 11% 23% 11% 2	2219
	11th to 20th	Day	43% 9% 9% 16% 20% 4	2234
	21st to end	Day	36% 11% 14% 30% 8% 1	2794
February	1st to 10th	Day	51% 7% 14% 16% 9% 3	1520
	11th to 20th	Day	49% 10% 14% 16% 8% 2	1608
	21st to end	Day	50% 8% 12% 17% 11% 1	1541
March	1st to 10th	Day	47% 9% 16% 16% 11%	3138
	11th to 20th	Day	33% 8% 21% 24% 13% 1	3397
	21st to end	Day	58% 9% 12% 14% 6%	3947
April	1st to 10th	Day	52% 10% 17% 14% 6%	2318
	11th to 20th	Day	54% 7% 12% 18% 8%	2440
	21st to end	Day	49% 10% 15% 18% 6% 1	2470
May	1st to 10th	Day	54% 8% 12% 20% 5%	4466
	11th to 20th	Day	46% 12% 16% 18% 8%	4698
	21st to end	Day	54% 12% 15% 13% 5% 1	5162
June	1st to 10th	Day	53% 10% 15% 15% 5% 2	2850
	11th to 20th	Day	57% 10% 15% 13% 5% 1	2850
	21st to end	Day	42% 12% 19% 20% 6% 1	2850
July	1st to 10th	Day	33% 9% 17% 24% 14% 4	4666
	11th to 20th	Day	30% 9% 19% 32% 8% 1	4659
	21st to end	Day	31% 8% 17% 26% 16% 3	4886
August	1st to 10th	Day	37% 9% 18% 28% 8%	4384
	11th to 20th	Day	33% 10% 23% 25% 8% 1	4201
	21st to end	Day	34% 8% 22% 29% 7% 1	4520
September	1st to 10th	Day	36% 8% 22% 21% 11% 3	2349
	11th to 20th	Day	41% 8% 14% 27% 9% 1	2109
	21st to end	Day	38% 9% 16% 23% 11% 3	2090
October	1st to 10th	Day	41% 8% 16% 24% 9% 1	2024
	11th to 20th	Day	42% 8% 18% 20% 10% 2	1710
	21st to end	Day	46% 9% 12% 21% 11% 1	1809
November	1st to 10th	Day	52% 8% 12% 17% 9% 2	1553
	11th to 20th	Day	45% 8% 13% 22% 11% 1	1373
	21st to end	Day	43% 9% 18% 18% 9% 3	1330
December	1st to 10th	Day	52% 7% 12% 15% 12% 2	1330
	11th to 20th	Day	46% 10% 17% 18% 8% 1	1684
	21st to end	Day	37% 8% 11% 20% 18% 5%	2442
January	1st to 10th	Night	52% 9% 13% 16% 8% 2	4726
	11th to 20th	Night	46% 8% 10% 16% 13% 6%	4740
	21st to end	Night	41% 11% 14% 22% 10% 1	4863
February	1st to 10th	Night	52% 8% 11% 17% 10% 2	2660
	11th to 20th	Night	51% 7% 14% 16% 11% 1	2469
	21st to end	Night	45% 5% 13% 22% 12% 2	1913
March	1st to 10th	Night	46% 12% 13% 20% 8% 1	3736
	11th to 20th	Night	34% 12% 19% 20% 13% 2	3583
	21st to end	Night	58% 10% 11% 14% 6% 1	3705
April	1st to 10th	Night	48% 9% 15% 19% 10% 1	1862
	11th to 20th	Night	52% 7% 14% 17% 9% 1	1691
	21st to end	Night	48% 9% 16% 20% 6% 1	1710
May	1st to 10th	Night	56% 7% 12% 20% 5%	2491
	11th to 20th	Night	40% 12% 16% 23% 10%	2199
	21st to end	Night	50% 16% 14% 15% 5% 1	2414
June	1st to 10th	Night	49% 10% 13% 18% 9% 1	1330
	11th to 20th	Night	53% 9% 14% 17% 5% 2	1330
	21st to end	Night	39% 12% 19% 23% 6% 1	1330
July	1st to 10th	Night	38% 9% 15% 22% 11% 4	2185
	11th to 20th	Night	26% 8% 23% 31% 8% 4	2178
	21st to end	Night	31% 7% 14% 32% 15% 1	2425
August	1st to 10th	Night	37% 9% 17% 30% 7%	2521
	11th to 20th	Night	34% 11% 24% 24% 6% 1	2699
	21st to end	Night	36% 6% 19% 30% 8% 1	3146
September	1st to 10th	Night	35% 7% 19% 23% 14% 3	1829
	11th to 20th	Night	40% 8% 15% 24% 10% 4	2071
	21st to end	Night	36% 7% 17% 24% 13% 3	2090
October	1st to 10th	Night	41% 7% 17% 23% 11% 1	2152
	11th to 20th	Night	42% 7% 16% 23% 10% 2	2470
	21st to end	Night	45% 9% 15% 21% 9% 1	2613
November	1st to 10th	Night	49% 8% 12% 19% 11% 2	2505
	11th to 20th	Night	45% 9% 16% 17% 11% 1	2806
	21st to end	Night	44% 9% 16% 19% 8% 4	2850
December	1st to 10th	Night	47% 6% 13% 20% 11% 3	2850
	11th to 20th	Night	48% 11% 14% 20% 6% 1	3507
	21st to end	Night	36% 7% 14% 22% 15% 6%	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 29% 32% 18% 11%	180
	11th to 20th	Day	6% 4 35% 34% 17% 4	180
	21st to end	Day	9% 7% 27% 33% 17% 7%	198
February	1st to 10th	Day	10% 11% 27% 36% 10% 6%	180
	11th to 20th	Day	11% 5% 29% 34% 17% 3	238
	21st to end	Day	4 7% 28% 39% 18% 3	353
March	1st to 10th	Day	8% 10% 35% 30% 13% 3	460
	11th to 20th	Day	8% 7% 33% 32% 15% 5%	460
	21st to end	Day	15% 9% 31% 26% 13% 4	506
April	1st to 10th	Day	12% 13% 34% 27% 12% 2	460
	11th to 20th	Day	16% 10% 27% 28% 14% 5%	452
	21st to end	Day	16% 13% 24% 29% 14% 4	460
May	1st to 10th	Day	19% 12% 22% 27% 15% 4	509
	11th to 20th	Day	14% 7% 24% 33% 19% 4	675
	21st to end	Day	19% 6% 19% 30% 20% 6%	734
June	1st to 10th	Day	18% 8% 24% 35% 13% 3	680
	11th to 20th	Day	22% 7% 24% 28% 14% 4	680
	21st to end	Day	11% 5% 23% 32% 20% 8%	680
July	1st to 10th	Day	13% 4 20% 33% 23% 8%	671
	11th to 20th	Day	15% 5% 19% 32% 24% 5%	668
	21st to end	Day	8% 5% 23% 32% 24% 7%	682
August	1st to 10th	Day	10% 5% 24% 34% 18% 8%	487
	11th to 20th	Day	8% 5% 24% 33% 25% 5%	477
	21st to end	Day	11% 7% 24% 31% 20% 7%	539
September	1st to 10th	Day	15% 7% 27% 29% 15% 7%	490
	11th to 20th	Day	20% 7% 22% 28% 18% 7%	490
	21st to end	Day	14% 10% 30% 28% 12% 4	490
October	1st to 10th	Day	14% 9% 25% 29% 17% 7%	428
	11th to 20th	Day	14% 8% 30% 28% 15% 5%	300
	21st to end	Day	14% 14% 29% 26% 13% 3	306
November	1st to 10th	Day	16% 5% 24% 38% 13% 4	270
	11th to 20th	Day	14% 10% 33% 28% 12% 2	201
	21st to end	Day	4 8% 29% 38% 13% 7%	180
December	1st to 10th	Day	7% 5% 29% 37% 17% 4	180
	11th to 20th	Day	6% 12% 34% 33% 12% 3	180
	21st to end	Day	6% 6% 27% 30% 25% 6%	198
January	1st to 10th	Night	10% 8% 33% 34% 13% 1	950
	11th to 20th	Night	8% 9% 33% 37% 13% 1	950
	21st to end	Night	11% 10% 33% 33% 11% 2	837
February	1st to 10th	Night	11% 9% 29% 33% 16% 3	760
	11th to 20th	Night	7% 8% 32% 37% 15% 1	744
	21st to end	Night	6% 4 29% 35% 19% 6%	628
March	1st to 10th	Night	9% 5% 30% 39% 14% 3	760
	11th to 20th	Night	8% 5% 32% 39% 13% 2	760
	21st to end	Night	13% 6% 28% 37% 14% 3	836
April	1st to 10th	Night	11% 7% 31% 35% 13% 2	722
	11th to 20th	Night	15% 6% 35% 33% 10% 1	563
	21st to end	Night	16% 11% 24% 35% 12% 1	570
May	1st to 10th	Night	20% 8% 23% 36% 11% 2	404
	11th to 20th	Night	13% 5% 24% 42% 15% 1	374
	21st to end	Night	22% 5% 20% 34% 18% 1	411
June	1st to 10th	Night	19% 6% 23% 38% 13% 1	380
	11th to 20th	Night	18% 5% 24% 35% 15% 2	380
	21st to end	Night	12% 3 19% 38% 25% 3	380
July	1st to 10th	Night	15% 2 16% 42% 23% 1	370
	11th to 20th	Night	14% 3 18% 44% 19% 1	368
	21st to end	Night	8% 4 17% 44% 25% 2	416
August	1st to 10th	Night	12% 4 16% 36% 29% 4	378
	11th to 20th	Night	12% 5% 14% 40% 27% 2	476
	21st to end	Night	13% 3 20% 42% 22%	627
September	1st to 10th	Night	15% 2 19% 40% 21% 2	689
	11th to 20th	Night	18% 3 21% 33% 22% 3	760
	21st to end	Night	13% 5% 30% 36% 15% 2	760
October	1st to 10th	Night	15% 5% 27% 36% 15% 2	760
	11th to 20th	Night	11% 4 31% 37% 14% 2	760
	21st to end	Night	12% 7% 33% 35% 12% 1	804
November	1st to 10th	Night	16% 6% 33% 31% 12% 2	840
	11th to 20th	Night	11% 8% 40% 31% 8% 1	950
	21st to end	Night	9% 5% 39% 35% 10% 3	950
December	1st to 10th	Night	11% 8% 32% 35% 12% 2	950
	11th to 20th	Night	8% 6% 36% 37% 12% 1	950
	21st to end	Night	10% 5% 33% 36% 13% 3	1045

Page generated at 2024-10-21 00:20:01. Version ac07

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