Bridgeport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bridgeport clear sky chart from 2005-11-06 to 2025-10-19.

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	18% 7% 2 5% 4 4 4 4 6% 7% 40%	126495
	Night	19% 7% 2 5% 4 3 4 3 4 6% 42%	123227
Transparency	Day	40% 6% 13% 22% 16% 3	130023
	Night	42% 5% 12% 22% 16% 3	127786
Seeing	Day	18% 6% 24% 30% 17% 4	16271
	Night	20% 8% 30% 29% 12% 1	25288

By Month

Percentage Cloud Cover NE (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	13% 6% 2 5% 3 3 4 4 6% 6% 48%	3597
	11th to 20th	Day	15% 9% 3 5% 4 4 4 4 5% 5% 43%	3570
	21st to end	Day	19% 7% 2 7% 4 4 4 3 4 5% 41%	4160
February	1st to 10th	Day	17% 7% 2 5% 5% 5% 5% 4 5% 7% 39%	1856
	11th to 20th	Day	15% 7% 2 5% 5% 3 4 3 5% 7% 43%	1948
	21st to end	Day	20% 8% 2 5% 4 4 4 3 5% 6% 39%	1650
March	1st to 10th	Day	23% 7% 2 4 3 3 3 3 4 6% 42%	4476
	11th to 20th	Day	14% 8% 2 5% 3 4 4 4 6% 7% 43%	4674
	21st to end	Day	20% 8% 2 5% 3 3 4 3 5% 6% 39%	5970
April	1st to 10th	Day	20% 8% 2 6% 4 3 4 4 6% 7% 37%	2400
	11th to 20th	Day	18% 6% 3 5% 4 4 4 3 5% 7% 41%	2374
	21st to end	Day	20% 5% 2 5% 4 4 4 4 5% 6% 41%	2485
May	1st to 10th	Day	30% 8% 2 4 3 3 4 3 6% 8% 28%	5886
	11th to 20th	Day	23% 8% 3 6% 4 3 4 3 5% 6% 37%	6166
	21st to end	Day	22% 5% 2 5% 4 4 5% 4 6% 7% 35%	6949
June	1st to 10th	Day	19% 5% 2 5% 4 4 4 4 7% 8% 38%	2800
	11th to 20th	Day	16% 6% 2 4 4 4 4 4 7% 9% 38%	2800
	21st to end	Day	14% 5% 2 5% 5% 4 4 4 6% 9% 40%	2800
July	1st to 10th	Day	14% 7% 2 7% 5% 4 5% 5% 7% 9% 36%	6360
	11th to 20th	Day	13% 7% 3 6% 4 5% 5% 5% 7% 10% 36%	6360
	21st to end	Day	14% 6% 2 6% 4 4 4 4 5% 7% 42%	6926
August	1st to 10th	Day	19% 6% 2 6% 4 5% 5% 4 6% 8% 35%	4362
	11th to 20th	Day	13% 6% 2 6% 4 3 4 4 6% 8% 45%	3850
	21st to end	Day	9% 4 2 5% 4 4 5% 4 7% 8% 48%	4312
September	1st to 10th	Day	14% 5% 2 5% 4 4 5% 3 5% 7% 46%	2400
	11th to 20th	Day	12% 5% 2 4 3 4 4 3 5% 6% 53%	2275
	21st to end	Day	20% 6% 2 6% 4 4 3 3 6% 7% 40%	2200
October	1st to 10th	Day	21% 6% 2 4 2 3 3 3 5% 7% 44%	2150
	11th to 20th	Day	17% 4 2 4 4 3 4 3 5% 7% 48%	1980
	21st to end	Day	21% 5% 1 5% 4 3 4 3 5% 7% 42%	1887
November	1st to 10th	Day	14% 6% 2 4 3 4 4 2 5% 5% 51%	1761
	11th to 20th	Day	18% 5% 2 4 3 3 3 3 4 5% 49%	1800
	21st to end	Day	17% 6% 2 5% 4 3 3 3 5% 7% 45%	1765
December	1st to 10th	Day	17% 6% 2 5% 3 3 4 3 5% 7% 45%	2600
	11th to 20th	Day	23% 6% 2 4 2 2 3 2 4 6% 46%	2986
	21st to end	Day	20% 10% 3 5% 4 3 4 3 4 6% 39%	3960
January	1st to 10th	Night	14% 6% 2 4 3 3 3 3 5% 7% 50%	6349
	11th to 20th	Night	15% 8% 3 6% 3 3 3 3 4 5% 47%	6315
	21st to end	Night	18% 9% 3 7% 4 4 4 3 4 5% 40%	6794
February	1st to 10th	Night	17% 9% 3 6% 4 4 4 3 5% 5% 41%	2541
	11th to 20th	Night	18% 8% 3 5% 4 3 3 2 5% 7% 42%	2338
	21st to end	Night	19% 8% 3 5% 5% 3 4 3 4 4 42%	1980
March	1st to 10th	Night	21% 9% 2 5% 3 3 3 2 4 6% 42%	5364
	11th to 20th	Night	18% 9% 2 5% 4 4 3 3 4 6% 43%	5283
	21st to end	Night	21% 9% 3 6% 4 3 3 3 5% 4 40%	4962
April	1st to 10th	Night	20% 8% 2 6% 4 4 4 4 4 6% 38%	2000
	11th to 20th	Night	21% 7% 2 5% 3 4 3 3 4 6% 41%	1975
	21st to end	Night	19% 6% 2 6% 4 3 3 3 5% 5% 43%	1915
May	1st to 10th	Night	29% 10% 3 6% 4 3 3 2 4 7% 28%	4054
	11th to 20th	Night	24% 10% 3 5% 3 3 4 3 5% 6% 34%	3769
	21st to end	Night	25% 7% 3 6% 3 4 4 3 5% 6% 36%	3926
June	1st to 10th	Night	19% 5% 2 6% 5% 4 4 3 5% 6% 40%	1600
	11th to 20th	Night	17% 7% 2 5% 3 4 4 3 6% 9% 40%	1600
	21st to end	Night	13% 6% 1 6% 5% 4 4 3 7% 9% 43%	1600
July	1st to 10th	Night	15% 8% 3 7% 5% 4 5% 4 5% 8% 37%	3600
	11th to 20th	Night	19% 8% 2 7% 4 4 4 4 6% 8% 33%	3600
	21st to end	Night	15% 6% 2 6% 4 4 5% 3 5% 7% 43%	3926
August	1st to 10th	Night	24% 5% 2 7% 4 4 5% 5% 6% 6% 32%	2740
	11th to 20th	Night	16% 6% 2 6% 4 5% 5% 4 5% 7% 39%	3197
	21st to end	Night	9% 4 2 4 3 4 4 3 5% 7% 55%	3586
September	1st to 10th	Night	14% 6% 2 6% 4 4 4 4 4 6% 46%	2000
	11th to 20th	Night	14% 5% 2 4 3 3 3 2 5% 7% 51%	2125
	21st to end	Night	19% 7% 3 4 3 4 4 3 3 5% 44%	2200
October	1st to 10th	Night	19% 7% 2 6% 4 3 4 2 5% 6% 43%	2247
	11th to 20th	Night	16% 5% 2 6% 3 4 3 2 4 6% 49%	2377
	21st to end	Night	22% 7% 2 5% 3 3 3 3 4 6% 42%	2710
November	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 5% 6% 50%	2537
	11th to 20th	Night	19% 7% 2 4 3 3 3 2 4 6% 48%	2600
	21st to end	Night	15% 6% 2 5% 4 3 4 3 5% 6% 47%	2633
December	1st to 10th	Night	17% 7% 2 5% 3 3 4 2 3 5% 50%	4580
	11th to 20th	Night	26% 6% 2 5% 3 3 3 2 4 4 43%	5208
	21st to end	Night	20% 8% 3 6% 3 3 3 2 4 4 43%	6996

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	33% 4 9% 31% 19% 3	3598
	11th to 20th	Day	40% 5% 13% 21% 15% 7%	3600
	21st to end	Day	45% 6% 10% 23% 15% 1	4160
February	1st to 10th	Day	44% 4 14% 22% 14% 1	1856
	11th to 20th	Day	40% 5% 10% 25% 17% 3	1957
	21st to end	Day	45% 5% 11% 21% 15% 3	1650
March	1st to 10th	Day	43% 4 12% 19% 13% 9%	4479
	11th to 20th	Day	36% 6% 16% 27% 13% 2	4674
	21st to end	Day	43% 5% 9% 15% 22% 6%	5970
April	1st to 10th	Day	42% 7% 11% 21% 15% 4	2400
	11th to 20th	Day	41% 5% 12% 21% 18% 3	2374
	21st to end	Day	41% 5% 11% 22% 17% 4	2485
May	1st to 10th	Day	51% 7% 17% 14% 9% 1	5897
	11th to 20th	Day	47% 6% 14% 19% 13% 2	6170
	21st to end	Day	43% 8% 12% 22% 13% 1	6949
June	1st to 10th	Day	40% 8% 14% 23% 15% 1	2800
	11th to 20th	Day	38% 8% 15% 24% 13% 1	2800
	21st to end	Day	36% 8% 16% 24% 15% 1	2800
July	1st to 10th	Day	41% 10% 13% 20% 15% 1	6290
	11th to 20th	Day	40% 8% 19% 22% 10% 1	6285
	21st to end	Day	39% 6% 12% 22% 20% 1	6728
August	1st to 10th	Day	44% 7% 17% 22% 9% 1	4348
	11th to 20th	Day	34% 6% 16% 31% 12% 1	3886
	21st to end	Day	30% 8% 13% 30% 18% 2	4312
September	1st to 10th	Day	35% 8% 13% 23% 19% 2	2400
	11th to 20th	Day	30% 6% 12% 25% 25% 2	2275
	21st to end	Day	43% 6% 11% 20% 17% 3	2200
October	1st to 10th	Day	33% 5% 11% 22% 23% 6%	3501
	11th to 20th	Day	27% 4 11% 23% 30% 4	3220
	21st to end	Day	30% 4 15% 25% 22% 3	3087
November	1st to 10th	Day	35% 6% 13% 23% 21% 2	1761
	11th to 20th	Day	37% 4 10% 22% 22% 3	1800
	21st to end	Day	39% 5% 14% 27% 12% 2	1765
December	1st to 10th	Day	39% 4 16% 28% 12% 1	2600
	11th to 20th	Day	41% 3 15% 21% 18% 3	2986
	21st to end	Day	46% 6% 9% 21% 15% 3	3960
January	1st to 10th	Night	35% 4 9% 26% 23% 3	6349
	11th to 20th	Night	40% 4 14% 21% 16% 6%	6360
	21st to end	Night	47% 4 10% 19% 15% 5%	6794
February	1st to 10th	Night	45% 6% 12% 23% 13% 2	2541
	11th to 20th	Night	44% 4 10% 21% 17% 5%	2340
	21st to end	Night	45% 4 8% 22% 17% 4	1980
March	1st to 10th	Night	45% 4 11% 18% 14% 8%	5374
	11th to 20th	Night	43% 5% 14% 22% 12% 4	5284
	21st to end	Night	48% 4 6% 12% 24% 6%	4962
April	1st to 10th	Night	47% 6% 10% 18% 16% 3	2000
	11th to 20th	Night	44% 5% 10% 19% 21% 1	1975
	21st to end	Night	43% 5% 9% 21% 17% 5%	1915
May	1st to 10th	Night	56% 7% 14% 12% 10% 1	4060
	11th to 20th	Night	51% 6% 14% 14% 13% 3	3770
	21st to end	Night	49% 6% 12% 21% 10% 1	3927
June	1st to 10th	Night	44% 6% 11% 20% 19% 2	1600
	11th to 20th	Night	40% 7% 15% 25% 12% 1	1600
	21st to end	Night	37% 9% 14% 25% 14% 2	1600
July	1st to 10th	Night	46% 7% 13% 21% 11% 1	3560
	11th to 20th	Night	47% 7% 16% 19% 10% 1	3552
	21st to end	Night	40% 6% 14% 23% 16% 1	3809
August	1st to 10th	Night	50% 8% 14% 17% 9% 1	2730
	11th to 20th	Night	42% 7% 13% 28% 9% 1	3227
	21st to end	Night	28% 7% 13% 32% 20% 1	3586
September	1st to 10th	Night	39% 6% 9% 26% 18% 2	2000
	11th to 20th	Night	34% 6% 10% 23% 25% 2	2125
	21st to end	Night	43% 6% 8% 20% 20% 3	2200
October	1st to 10th	Night	38% 6% 10% 23% 19% 3	3676
	11th to 20th	Night	26% 4 10% 26% 30% 4	3876
	21st to end	Night	32% 5% 13% 27% 21% 2	4460
November	1st to 10th	Night	36% 6% 12% 23% 20% 4	2537
	11th to 20th	Night	40% 5% 8% 23% 20% 4	2600
	21st to end	Night	38% 5% 13% 30% 13% 2	2633
December	1st to 10th	Night	39% 3 12% 30% 14% 2	4580
	11th to 20th	Night	47% 3 11% 19% 17% 3	5208
	21st to end	Night	45% 4 11% 20% 16% 4	6996

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	18% 17% 35% 23% 8% 1	200
	11th to 20th	Day	16% 15% 47% 18% 5% 1	200
	21st to end	Day	20% 7% 41% 23% 8% 1	263
February	1st to 10th	Day	21% 10% 39% 25% 4	356
	11th to 20th	Day	18% 13% 43% 24% 2	496
	21st to end	Day	22% 12% 36% 23% 6%	414
March	1st to 10th	Day	17% 10% 37% 30% 6%	500
	11th to 20th	Day	15% 7% 41% 29% 7% 1	500
	21st to end	Day	21% 10% 35% 26% 7% 1	550
April	1st to 10th	Day	23% 9% 33% 24% 9% 1	500
	11th to 20th	Day	19% 7% 32% 30% 11% 1	492
	21st to end	Day	23% 6% 25% 33% 11% 1	500
May	1st to 10th	Day	28% 4 24% 33% 9% 2	503
	11th to 20th	Day	19% 4 24% 34% 18% 1	527
	21st to end	Day	18% 2 15% 34% 25% 6%	573
June	1st to 10th	Day	18% 3 15% 35% 24% 5%	530
	11th to 20th	Day	17% 3 17% 36% 23% 4	530
	21st to end	Day	14% 2 16% 35% 28% 5%	530
July	1st to 10th	Day	14% 2 13% 31% 32% 9%	525
	11th to 20th	Day	11% 3 9% 34% 34% 9%	524
	21st to end	Day	13% 4 12% 37% 30% 3	576
August	1st to 10th	Day	11% 3 10% 38% 29% 9%	526
	11th to 20th	Day	14% 1 8% 34% 33% 9%	519
	21st to end	Day	11% 2 14% 38% 26% 9%	583
September	1st to 10th	Day	18% 2 16% 29% 25% 10%	530
	11th to 20th	Day	14% 3 16% 28% 29% 10%	530
	21st to end	Day	22% 4 19% 31% 20% 4	530
October	1st to 10th	Day	23% 5% 18% 26% 20% 9%	530
	11th to 20th	Day	17% 7% 27% 30% 16% 3	522
	21st to end	Day	23% 9% 26% 28% 12% 2	432
November	1st to 10th	Day	14% 9% 26% 32% 15% 4	395
	11th to 20th	Day	19% 11% 36% 26% 8%	400
	21st to end	Day	20% 12% 32% 28% 9%	365
December	1st to 10th	Day	17% 13% 37% 24% 9% 1	200
	11th to 20th	Day	27% 14% 30% 24% 6%	200
	21st to end	Day	22% 8% 36% 23% 10% 1	220
January	1st to 10th	Night	19% 16% 40% 21% 4	800
	11th to 20th	Night	23% 13% 36% 24% 3	800
	21st to end	Night	19% 14% 40% 25% 2	880
February	1st to 10th	Night	21% 11% 40% 27% 2	800
	11th to 20th	Night	22% 12% 43% 21% 2	783
	21st to end	Night	22% 12% 38% 22% 5%	660
March	1st to 10th	Night	22% 9% 39% 26% 5%	800
	11th to 20th	Night	20% 9% 38% 27% 6% 1	800
	21st to end	Night	22% 8% 38% 26% 6%	880
April	1st to 10th	Night	22% 8% 35% 29% 5% 1	800
	11th to 20th	Night	24% 5% 31% 31% 9%	791
	21st to end	Night	20% 5% 32% 33% 8% 1	715
May	1st to 10th	Night	27% 6% 25% 31% 11% 1	600
	11th to 20th	Night	22% 4 31% 32% 11%	484
	21st to end	Night	22% 3 15% 35% 22% 2	433
June	1st to 10th	Night	19% 3 23% 35% 18% 2	400
	11th to 20th	Night	19% 3 16% 42% 20% 1	400
	21st to end	Night	14% 1 16% 46% 22% 1	400
July	1st to 10th	Night	14% 1 16% 39% 28% 2	390
	11th to 20th	Night	14% 2 12% 43% 26% 3	388
	21st to end	Night	15% 2 14% 45% 23% 1	438
August	1st to 10th	Night	12% 1 15% 44% 26% 2	487
	11th to 20th	Night	15% 3 13% 36% 30% 4	790
	21st to end	Night	13% 2 17% 35% 29% 4	880
September	1st to 10th	Night	17% 2 22% 33% 22% 4	800
	11th to 20th	Night	16% 3 18% 35% 22% 6%	800
	21st to end	Night	21% 4 22% 32% 18% 3	800
October	1st to 10th	Night	22% 7% 26% 24% 17% 4	800
	11th to 20th	Night	18% 9% 30% 32% 10% 1	793
	21st to end	Night	25% 9% 33% 25% 8% 1	836
November	1st to 10th	Night	16% 8% 34% 29% 12% 2	780
	11th to 20th	Night	22% 11% 35% 24% 8% 1	800
	21st to end	Night	18% 15% 34% 27% 7% 1	800
December	1st to 10th	Night	24% 12% 35% 22% 6% 1	800
	11th to 20th	Night	24% 13% 35% 25% 4	800
	21st to end	Night	24% 12% 37% 24% 4	880

Page generated at 2025-10-16 01:50:24. Version ac07

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