Flagler Reservoir SWA
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Flagler Reservoir SWA clear sky chart from 2005-11-06 to 2026-03-03.

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	5% 5% 2 4 3 3 4 3 5% 7% 58%	139513
	Night	6% 6% 2 5% 4 4 4 3 5% 7% 54%	139095
Transparency	Day	24% 5% 10% 26% 25% 10%	134489
	Night	28% 5% 10% 24% 23% 9%	135142
Seeing	Day	8% 9% 28% 32% 18% 5%	17339
	Night	8% 8% 36% 37% 10% 1	27455

By Month

Percentage Cloud Cover SW (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 9% 3 7% 3 3 3 3 5% 5% 56%	4720
	11th to 20th	Day	2 6% 2 5% 4 3 3 3 5% 6% 62%	4740
	21st to end	Day	3 7% 2 6% 3 3 3 2 4 6% 61%	5623
February	1st to 10th	Day	3 7% 2 7% 4 4 4 4 5% 6% 55%	2041
	11th to 20th	Day	2 7% 2 6% 6% 5% 4 2 5% 7% 55%	2049
	21st to end	Day	3 5% 3 7% 3 3 3 3 4 6% 60%	1730
March	1st to 10th	Day	3 7% 2 4 3 3 3 3 4 7% 60%	4520
	11th to 20th	Day	6% 5% 2 5% 4 3 3 3 5% 7% 57%	4656
	21st to end	Day	4 5% 2 5% 3 4 4 4 6% 9% 55%	5969
April	1st to 10th	Day	7% 6% 2 5% 3 3 3 3 5% 9% 54%	2400
	11th to 20th	Day	10% 5% 3 5% 4 4 4 4 5% 7% 50%	2371
	21st to end	Day	9% 7% 2 5% 5% 4 4 4 6% 8% 47%	2449
May	1st to 10th	Day	9% 6% 2 5% 4 3 4 3 5% 6% 54%	5900
	11th to 20th	Day	6% 4 2 4 3 3 4 4 6% 8% 57%	5862
	21st to end	Day	11% 5% 1 4 3 3 4 4 6% 8% 51%	6897
June	1st to 10th	Day	5% 3 1 3 3 4 4 4 7% 9% 55%	2800
	11th to 20th	Day	6% 4 1 3 2 3 4 4 6% 8% 60%	2800
	21st to end	Day	3 4 2 5% 3 4 4 4 6% 8% 57%	2800
July	1st to 10th	Day	5% 3 1 4 4 4 4 4 7% 8% 57%	6339
	11th to 20th	Day	2 2 1 4 3 4 4 4 8% 11% 57%	6340
	21st to end	Day	4 3 1 4 3 4 4 4 7% 10% 54%	6903
August	1st to 10th	Day	9% 4 2 4 3 3 4 4 7% 10% 51%	5659
	11th to 20th	Day	3 2 1 3 3 3 5% 4 6% 9% 59%	5366
	21st to end	Day	7% 4 2 5% 4 4 4 5% 6% 8% 50%	5984
September	1st to 10th	Day	5% 3 1 3 3 3 4 3 5% 6% 64%	2400
	11th to 20th	Day	6% 3 1 4 3 3 3 3 6% 7% 63%	2273
	21st to end	Day	6% 4 1 3 2 2 3 2 4 6% 66%	2200
October	1st to 10th	Day	5% 2 1 2 1 2 2 1 3 4 76%	3569
	11th to 20th	Day	6% 3 1 4 3 3 2 2 4 6% 66%	3250
	21st to end	Day	5% 5% 2 3 2 2 2 2 3 4 69%	3230
November	1st to 10th	Day	4 4 1 3 3 3 3 3 4 7% 65%	1853
	11th to 20th	Day	2 5% 2 4 3 2 2 3 5% 6% 66%	1890
	21st to end	Day	4 6% 2 5% 3 3 3 3 4 6% 62%	1890
December	1st to 10th	Day	2 7% 2 4 2 2 2 2 4 5% 68%	2842
	11th to 20th	Day	2 4 2 4 3 3 3 3 4 8% 66%	3106
	21st to end	Day	4 8% 3 7% 4 3 3 3 4 6% 55%	4092
January	1st to 10th	Night	3 9% 3 7% 4 3 3 3 5% 6% 54%	8201
	11th to 20th	Night	2 6% 2 6% 4 3 3 3 4 6% 62%	8250
	21st to end	Night	3 6% 2 6% 4 4 3 3 4 5% 59%	8636
February	1st to 10th	Night	4 6% 2 6% 3 3 4 3 6% 7% 56%	2578
	11th to 20th	Night	4 8% 3 7% 4 4 4 4 6% 8% 48%	2458
	21st to end	Night	3 6% 2 5% 3 3 2 3 4 6% 61%	2076
March	1st to 10th	Night	4 7% 3 5% 3 3 3 2 4 5% 60%	5398
	11th to 20th	Night	7% 8% 2 5% 3 3 3 3 4 6% 56%	5319
	21st to end	Night	7% 6% 2 6% 4 4 4 4 6% 9% 49%	4984
April	1st to 10th	Night	7% 8% 2 5% 4 4 4 4 6% 6% 50%	2000
	11th to 20th	Night	11% 7% 3 6% 3 4 3 3 5% 8% 47%	1977
	21st to end	Night	12% 7% 2 6% 5% 3 4 3 6% 7% 45%	1950
May	1st to 10th	Night	11% 7% 2 6% 4 4 5% 3 4 8% 45%	4080
	11th to 20th	Night	8% 5% 2 5% 3 5% 4 4 6% 9% 49%	4053
	21st to end	Night	16% 8% 2 5% 4 4 4 4 6% 7% 42%	3984
June	1st to 10th	Night	6% 3 2 5% 4 3 3 4 8% 10% 52%	1600
	11th to 20th	Night	5% 5% 1 4 3 5% 4 4 8% 9% 52%	1600
	21st to end	Night	4 5% 2 6% 5% 5% 5% 5% 8% 8% 48%	1600
July	1st to 10th	Night	5% 4 2 6% 5% 5% 5% 5% 8% 9% 47%	3640
	11th to 20th	Night	6% 4 2 5% 4 5% 6% 5% 7% 9% 46%	3640
	21st to end	Night	4 4 2 6% 5% 5% 6% 5% 7% 9% 46%	3970
August	1st to 10th	Night	10% 7% 2 8% 6% 5% 6% 5% 7% 9% 36%	4122
	11th to 20th	Night	6% 5% 2 6% 4 5% 5% 5% 8% 10% 44%	4483
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 7% 8% 42%	4993
September	1st to 10th	Night	6% 4 1 4 3 3 5% 4 7% 7% 56%	2000
	11th to 20th	Night	5% 4 1 4 3 3 3 4 6% 8% 60%	2125
	21st to end	Night	6% 4 1 4 2 2 3 3 4 5% 65%	2200
October	1st to 10th	Night	6% 4 1 3 2 3 3 2 4 5% 67%	3608
	11th to 20th	Night	7% 5% 2 3 3 2 3 3 4 5% 64%	3898
	21st to end	Night	5% 5% 2 4 3 3 3 2 4 5% 65%	4536
November	1st to 10th	Night	3 3 1 4 3 3 3 3 5% 7% 65%	2665
	11th to 20th	Night	3 4 1 3 2 2 3 2 4 6% 68%	2730
	21st to end	Night	4 6% 3 5% 3 3 2 2 5% 6% 61%	2730
December	1st to 10th	Night	2 4 2 4 3 2 3 2 3 5% 71%	4562
	11th to 20th	Night	2 4 2 4 3 3 4 4 5% 7% 62%	5321
	21st to end	Night	4 8% 3 6% 3 4 4 4 5% 8% 51%	7128

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	30% 4 6% 31% 21% 8%	4723
	11th to 20th	Day	23% 5% 9% 25% 28% 10%	4740
	21st to end	Day	26% 4 8% 27% 27% 9%	5623
February	1st to 10th	Day	29% 5% 10% 27% 21% 9%	2041
	11th to 20th	Day	30% 4 9% 27% 23% 8%	2059
	21st to end	Day	26% 3 8% 22% 26% 15%	1730
March	1st to 10th	Day	24% 4 5% 19% 32% 15%	4520
	11th to 20th	Day	26% 4 7% 23% 32% 8%	4656
	21st to end	Day	23% 7% 11% 40% 17% 3	5969
April	1st to 10th	Day	27% 5% 10% 24% 25% 8%	2400
	11th to 20th	Day	31% 6% 11% 24% 18% 9%	2374
	21st to end	Day	32% 7% 12% 25% 21% 4	2449
May	1st to 10th	Day	29% 6% 11% 27% 18% 8%	5900
	11th to 20th	Day	22% 7% 12% 24% 25% 10%	5866
	21st to end	Day	29% 7% 14% 24% 19% 7%	6898
June	1st to 10th	Day	23% 7% 18% 29% 18% 6%	2800
	11th to 20th	Day	21% 6% 11% 24% 23% 14%	2800
	21st to end	Day	22% 6% 11% 23% 26% 12%	2800
July	1st to 10th	Day	22% 6% 10% 21% 30% 12%	6271
	11th to 20th	Day	19% 7% 17% 26% 24% 6%	6265
	21st to end	Day	23% 6% 16% 21% 20% 13%	6705
August	1st to 10th	Day	28% 7% 16% 29% 16% 5%	4114
	11th to 20th	Day	22% 6% 15% 23% 27% 7%	3882
	21st to end	Day	22% 5% 12% 26% 23% 12%	4311
September	1st to 10th	Day	20% 5% 10% 24% 27% 15%	2400
	11th to 20th	Day	19% 5% 7% 22% 30% 16%	2273
	21st to end	Day	21% 3 6% 23% 33% 14%	2200
October	1st to 10th	Day	14% 3 6% 16% 35% 26%	3569
	11th to 20th	Day	21% 3 7% 28% 30% 10%	3250
	21st to end	Day	21% 3 5% 25% 34% 13%	3230
November	1st to 10th	Day	19% 4 9% 27% 26% 14%	1853
	11th to 20th	Day	19% 3 6% 28% 33% 11%	1890
	21st to end	Day	26% 3 8% 22% 28% 13%	1890
December	1st to 10th	Day	20% 2 8% 31% 31% 8%	2842
	11th to 20th	Day	19% 2 7% 34% 33% 5%	3104
	21st to end	Day	28% 6% 7% 27% 23% 8%	4092
January	1st to 10th	Night	31% 4 7% 30% 23% 5%	8202
	11th to 20th	Night	24% 5% 10% 23% 26% 12%	8250
	21st to end	Night	28% 4 8% 26% 24% 10%	8636
February	1st to 10th	Night	27% 5% 11% 27% 21% 9%	2578
	11th to 20th	Night	33% 5% 12% 26% 20% 5%	2458
	21st to end	Night	25% 4 6% 23% 28% 14%	2076
March	1st to 10th	Night	26% 4 6% 17% 31% 17%	5398
	11th to 20th	Night	29% 5% 10% 16% 28% 13%	5319
	21st to end	Night	30% 8% 14% 31% 16% 2	4984
April	1st to 10th	Night	32% 6% 10% 23% 21% 8%	2000
	11th to 20th	Night	34% 6% 11% 24% 20% 5%	1977
	21st to end	Night	37% 7% 11% 24% 18% 3	1950
May	1st to 10th	Night	35% 9% 14% 26% 12% 4	4080
	11th to 20th	Night	28% 9% 15% 24% 19% 5%	4054
	21st to end	Night	38% 9% 16% 21% 12% 3	3984
June	1st to 10th	Night	25% 9% 24% 24% 15% 4	1600
	11th to 20th	Night	26% 8% 15% 22% 19% 10%	1600
	21st to end	Night	30% 7% 11% 23% 20% 8%	1600
July	1st to 10th	Night	30% 7% 13% 26% 21% 3	3600
	11th to 20th	Night	32% 7% 18% 20% 19% 4	3592
	21st to end	Night	32% 7% 15% 17% 19% 9%	3856
August	1st to 10th	Night	46% 7% 14% 20% 11% 3	3004
	11th to 20th	Night	38% 8% 13% 22% 16% 4	3243
	21st to end	Night	28% 7% 13% 27% 16% 9%	3597
September	1st to 10th	Night	24% 7% 11% 21% 26% 11%	2000
	11th to 20th	Night	20% 6% 11% 23% 27% 13%	2125
	21st to end	Night	22% 4 8% 22% 32% 12%	2200
October	1st to 10th	Night	20% 4 7% 18% 30% 21%	3608
	11th to 20th	Night	23% 4 7% 25% 29% 12%	3898
	21st to end	Night	23% 3 7% 24% 30% 12%	4536
November	1st to 10th	Night	19% 4 9% 27% 28% 14%	2665
	11th to 20th	Night	19% 3 8% 27% 31% 12%	2730
	21st to end	Night	25% 3 8% 24% 28% 12%	2730
December	1st to 10th	Night	18% 3 8% 33% 29% 9%	4562
	11th to 20th	Night	22% 3 6% 32% 32% 5%	5322
	21st to end	Night	30% 6% 8% 26% 26% 5%	7128

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	8% 9% 36% 33% 13% 2	330
	11th to 20th	Day	11% 13% 32% 33% 10% 2	330
	21st to end	Day	7% 10% 39% 31% 10% 2	363
February	1st to 10th	Day	7% 8% 50% 27% 7% 2	330
	11th to 20th	Day	5% 11% 45% 31% 8% 2	330
	21st to end	Day	5% 14% 44% 27% 8% 2	273
March	1st to 10th	Day	7% 11% 34% 29% 16% 2	306
	11th to 20th	Day	12% 11% 33% 28% 14% 1	309
	21st to end	Day	11% 17% 35% 27% 8% 1	550
April	1st to 10th	Day	13% 15% 38% 22% 10% 2	500
	11th to 20th	Day	13% 19% 35% 24% 8% 1	492
	21st to end	Day	15% 17% 32% 24% 11% 1	549
May	1st to 10th	Day	13% 12% 28% 33% 13% 2	703
	11th to 20th	Day	15% 9% 30% 25% 16% 4	725
	21st to end	Day	11% 11% 31% 28% 15% 4	789
June	1st to 10th	Day	7% 6% 24% 30% 26% 8%	730
	11th to 20th	Day	7% 7% 28% 36% 18% 4	730
	21st to end	Day	5% 5% 27% 38% 21% 5%	730
July	1st to 10th	Day	7% 3 17% 38% 28% 7%	721
	11th to 20th	Day	3 2 14% 40% 31% 9%	718
	21st to end	Day	6% 1 12% 37% 32% 10%	794
August	1st to 10th	Day	5% 2 15% 37% 30% 9%	638
	11th to 20th	Day	3 3 21% 39% 27% 7%	517
	21st to end	Day	4 2 19% 44% 24% 7%	583
September	1st to 10th	Day	4 3 19% 38% 25% 9%	530
	11th to 20th	Day	4 4 20% 38% 24% 9%	403
	21st to end	Day	11% 4 22% 25% 27% 11%	330
October	1st to 10th	Day	10% 6% 21% 28% 24% 11%	330
	11th to 20th	Day	6% 9% 35% 31% 13% 7%	330
	21st to end	Day	10% 11% 30% 26% 17% 6%	363
November	1st to 10th	Day	6% 11% 34% 32% 14% 3	330
	11th to 20th	Day	5% 7% 35% 31% 18% 4	330
	21st to end	Day	9% 14% 29% 33% 12% 3	330
December	1st to 10th	Day	7% 12% 36% 33% 8% 4	330
	11th to 20th	Day	7% 14% 37% 29% 12% 1	330
	21st to end	Day	8% 14% 36% 33% 9% 1	363
January	1st to 10th	Night	7% 7% 40% 35% 9% 1	1050
	11th to 20th	Night	7% 10% 39% 33% 10% 1	1050
	21st to end	Night	6% 8% 43% 34% 9%	1021
February	1st to 10th	Night	8% 9% 46% 33% 5%	840
	11th to 20th	Night	8% 10% 47% 28% 6%	824
	21st to end	Night	6% 9% 47% 34% 4	692
March	1st to 10th	Night	7% 12% 38% 36% 7%	808
	11th to 20th	Night	11% 7% 42% 30% 8% 1	766
	21st to end	Night	9% 10% 43% 33% 4	660
April	1st to 10th	Night	12% 14% 44% 27% 4	600
	11th to 20th	Night	16% 13% 39% 28% 3	593
	21st to end	Night	14% 14% 35% 30% 7% 1	600
May	1st to 10th	Night	13% 12% 34% 32% 9%	600
	11th to 20th	Night	15% 9% 33% 33% 9% 1	591
	21st to end	Night	14% 12% 38% 29% 7%	650
June	1st to 10th	Night	8% 8% 32% 39% 13% 1	600
	11th to 20th	Night	6% 7% 43% 36% 8%	600
	21st to end	Night	6% 5% 32% 45% 12% 1	600
July	1st to 10th	Night	6% 3 26% 49% 16% 1	585
	11th to 20th	Night	6% 2 16% 53% 21% 2	582
	21st to end	Night	6% 2 19% 47% 25% 2	657
August	1st to 10th	Night	7% 2 21% 45% 22% 2	597
	11th to 20th	Night	6% 4 24% 47% 18% 1	594
	21st to end	Night	7% 1 23% 51% 17% 1	660
September	1st to 10th	Night	7% 2 27% 47% 17% 1	600
	11th to 20th	Night	7% 5% 29% 43% 14% 2	600
	21st to end	Night	7% 5% 30% 43% 14% 1	600
October	1st to 10th	Night	12% 6% 32% 37% 13% 1	605
	11th to 20th	Night	7% 8% 36% 35% 13% 2	800
	21st to end	Night	9% 8% 32% 36% 13% 2	1050
November	1st to 10th	Night	5% 7% 37% 39% 11% 1	1025
	11th to 20th	Night	6% 8% 39% 37% 9% 1	1050
	21st to end	Night	7% 9% 34% 37% 11% 2	1050
December	1st to 10th	Night	5% 9% 42% 33% 10% 1	1050
	11th to 20th	Night	7% 9% 41% 34% 9% 1	1050
	21st to end	Night	7% 13% 42% 32% 6%	1155

Page generated at 2026-02-27 23:40:21. Version ac07

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