New Haven
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Haven clear sky chart from 2005-11-06 to 2024-11-05.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	101084
	Night	15% 10% 4 8% 5% 4 4 4 5% 7% 35%	97935
Transparency	Day	46% 7% 13% 21% 12% 1	104700
	Night	47% 6% 12% 21% 12% 1	102459
Seeing	Day	16% 8% 27% 27% 16% 6%	15319
	Night	18% 7% 29% 31% 13% 2	24881

By Month

Percentage Cloud Cover SE (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	17% 18% 6% 10% 5% 4 4 3 5% 5% 24%	2527
	11th to 20th	Day	15% 19% 5% 13% 7% 7% 6% 4 5% 6% 14%	2561
	21st to end	Day	28% 19% 6% 9% 6% 3 4 3 3 4 15%	3124
February	1st to 10th	Day	15% 15% 5% 12% 8% 5% 5% 4 4 5% 22%	1710
	11th to 20th	Day	13% 14% 5% 11% 8% 5% 5% 3 4 6% 26%	1757
	21st to end	Day	14% 16% 5% 11% 7% 4 4 3 4 5% 27%	1570
March	1st to 10th	Day	17% 15% 5% 10% 5% 5% 3 3 3 6% 28%	3238
	11th to 20th	Day	13% 13% 4 9% 6% 5% 5% 4 5% 6% 32%	3480
	21st to end	Day	19% 13% 4 8% 5% 4 4 3 5% 5% 30%	3815
April	1st to 10th	Day	14% 13% 4 9% 6% 4 4 3 5% 6% 32%	2171
	11th to 20th	Day	17% 9% 3 7% 5% 5% 4 4 5% 7% 34%	2437
	21st to end	Day	18% 9% 3 8% 5% 4 4 3 4 7% 34%	2470
May	1st to 10th	Day	17% 7% 3 7% 5% 4 4 4 5% 7% 35%	4082
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 7% 35%	4081
	21st to end	Day	9% 5% 2 7% 5% 5% 4 4 5% 8% 46%	4502
June	1st to 10th	Day	10% 5% 3 8% 4 5% 5% 4 7% 9% 40%	2795
	11th to 20th	Day	10% 5% 2 7% 5% 5% 5% 4 8% 9% 42%	2850
	21st to end	Day	9% 6% 2 6% 5% 6% 5% 5% 7% 10% 39%	2834
July	1st to 10th	Day	10% 6% 2 8% 5% 5% 6% 4 7% 10% 38%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 7% 10% 45%	4440
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 5% 8% 10% 39%	4472
August	1st to 10th	Day	12% 5% 2 6% 4 5% 5% 5% 7% 9% 40%	4104
	11th to 20th	Day	9% 5% 2 7% 5% 5% 6% 5% 8% 10% 38%	4044
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 9% 39%	4532
September	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 6% 9% 41%	2146
	11th to 20th	Day	9% 5% 2 6% 3 5% 5% 5% 6% 8% 48%	2090
	21st to end	Day	14% 7% 3 6% 4 5% 5% 5% 6% 8% 36%	2090
October	1st to 10th	Day	12% 7% 3 7% 4 4 5% 3 6% 7% 43%	2009
	11th to 20th	Day	17% 9% 3 7% 5% 5% 4 4 4 7% 34%	1900
	21st to end	Day	18% 11% 4 8% 4 3 5% 3 4 7% 30%	1967
November	1st to 10th	Day	12% 9% 3 8% 4 6% 5% 4 6% 7% 37%	1708
	11th to 20th	Day	14% 11% 4 7% 6% 4 5% 4 6% 6% 33%	1710
	21st to end	Day	19% 11% 5% 9% 6% 4 4 3 6% 6% 28%	1521
December	1st to 10th	Day	15% 14% 6% 13% 6% 5% 4 3 6% 6% 22%	1520
	11th to 20th	Day	17% 16% 4 9% 4 5% 4 4 7% 6% 24%	1814
	21st to end	Day	26% 20% 7% 10% 4 4 4 3 4 6% 12%	2573
January	1st to 10th	Night	16% 16% 5% 10% 5% 4 4 3 5% 5% 25%	4428
	11th to 20th	Night	14% 17% 7% 13% 6% 5% 6% 4 4 5% 18%	4404
	21st to end	Night	24% 18% 8% 10% 5% 3 3 2 3 4 19%	4532
February	1st to 10th	Night	15% 16% 5% 12% 6% 5% 5% 4 5% 5% 23%	2470
	11th to 20th	Night	14% 14% 5% 9% 7% 4 5% 5% 5% 5% 28%	2307
	21st to end	Night	18% 12% 4 9% 5% 5% 5% 4 5% 5% 29%	1884
March	1st to 10th	Night	16% 14% 4 8% 5% 3 3 3 4 6% 34%	3614
	11th to 20th	Night	10% 9% 3 7% 5% 5% 5% 4 6% 7% 40%	3480
	21st to end	Night	17% 9% 3 7% 4 4 4 3 4 6% 38%	3817
April	1st to 10th	Night	18% 10% 3 6% 5% 4 4 4 5% 6% 35%	2024
	11th to 20th	Night	18% 8% 3 5% 4 4 4 4 5% 7% 37%	1690
	21st to end	Night	16% 9% 3 5% 5% 3 4 4 6% 8% 37%	1710
May	1st to 10th	Night	17% 7% 3 7% 5% 3 4 3 6% 8% 37%	2813
	11th to 20th	Night	14% 8% 3 8% 5% 4 4 4 5% 7% 40%	2812
	21st to end	Night	10% 5% 2 6% 4 4 5% 3 5% 7% 49%	3048
June	1st to 10th	Night	10% 6% 2 6% 4 3 4 4 6% 8% 47%	1381
	11th to 20th	Night	9% 6% 2 6% 3 4 5% 5% 6% 7% 46%	1330
	21st to end	Night	8% 6% 2 6% 5% 4 3 4 5% 8% 50%	1340
July	1st to 10th	Night	8% 4 2 5% 4 4 4 4 7% 11% 49%	2530
	11th to 20th	Night	9% 4 1 4 3 3 4 3 6% 9% 53%	2530
	21st to end	Night	5% 4 2 5% 4 5% 5% 4 9% 10% 46%	3077
August	1st to 10th	Night	12% 5% 2 6% 4 4 4 3 5% 8% 46%	2825
	11th to 20th	Night	9% 6% 2 6% 4 4 5% 4 6% 8% 46%	2785
	21st to end	Night	8% 5% 2 6% 5% 4 5% 4 5% 7% 49%	3124
September	1st to 10th	Night	9% 6% 3 6% 5% 5% 4 3 5% 8% 47%	2012
	11th to 20th	Night	9% 5% 2 5% 3 3 3 3 5% 8% 54%	2090
	21st to end	Night	15% 6% 2 6% 4 5% 3 4 5% 7% 43%	2090
October	1st to 10th	Night	13% 6% 3 7% 3 3 4 3 5% 6% 47%	2171
	11th to 20th	Night	19% 8% 3 8% 4 5% 4 3 5% 6% 36%	2280
	21st to end	Night	20% 9% 3 6% 4 5% 5% 4 5% 7% 32%	2627
November	1st to 10th	Night	13% 7% 2 7% 4 4 4 3 6% 7% 42%	2470
	11th to 20th	Night	15% 10% 3 8% 5% 5% 4 4 7% 7% 32%	2470
	21st to end	Night	19% 14% 4 8% 5% 3 4 3 5% 6% 29%	2655
December	1st to 10th	Night	18% 14% 4 10% 6% 4 5% 5% 5% 6% 22%	2660
	11th to 20th	Night	14% 14% 5% 10% 6% 5% 5% 3 5% 7% 26%	3379
	21st to end	Night	28% 20% 6% 10% 5% 4 4 3 3 4 14%	5076

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	61% 8% 13% 12% 5% 1	2528
	11th to 20th	Day	70% 9% 10% 8% 3	2561
	21st to end	Day	72% 7% 11% 7% 3	3124
February	1st to 10th	Day	64% 7% 9% 14% 6%	1710
	11th to 20th	Day	59% 4 12% 16% 7% 1	1766
	21st to end	Day	58% 6% 12% 17% 6% 1	1570
March	1st to 10th	Day	57% 6% 12% 19% 5% 1	3238
	11th to 20th	Day	50% 7% 14% 19% 8% 1	3480
	21st to end	Day	54% 6% 14% 15% 10% 2	3815
April	1st to 10th	Day	50% 6% 12% 19% 11% 1	2171
	11th to 20th	Day	48% 5% 11% 20% 13% 2	2437
	21st to end	Day	49% 6% 13% 18% 13% 2	2470
May	1st to 10th	Day	44% 7% 13% 22% 12% 2	4120
	11th to 20th	Day	43% 9% 16% 21% 9% 1	4085
	21st to end	Day	35% 7% 12% 18% 22% 6%	4516
June	1st to 10th	Day	38% 8% 12% 26% 13% 2	2795
	11th to 20th	Day	37% 7% 14% 23% 16% 3	2850
	21st to end	Day	37% 8% 14% 24% 15% 2	2834
July	1st to 10th	Day	40% 7% 14% 22% 16% 2	4371
	11th to 20th	Day	30% 8% 15% 33% 14% 1	4365
	21st to end	Day	34% 10% 17% 16% 21% 2	4330
August	1st to 10th	Day	36% 9% 14% 24% 16% 1	4091
	11th to 20th	Day	36% 9% 13% 31% 10% 1	4083
	21st to end	Day	38% 7% 14% 27% 14% 1	4531
September	1st to 10th	Day	37% 9% 15% 24% 14% 2	2146
	11th to 20th	Day	31% 9% 12% 31% 16% 1	2090
	21st to end	Day	43% 8% 13% 23% 12% 1	2090
October	1st to 10th	Day	31% 6% 12% 33% 18% 1	3334
	11th to 20th	Day	41% 5% 12% 25% 17%	3140
	21st to end	Day	45% 6% 14% 22% 12% 1	3217
November	1st to 10th	Day	43% 8% 14% 24% 10% 1	1708
	11th to 20th	Day	50% 7% 13% 18% 10% 1	1710
	21st to end	Day	56% 7% 13% 17% 6% 1	1521
December	1st to 10th	Day	62% 8% 11% 15% 4	1520
	11th to 20th	Day	58% 8% 14% 15% 6%	1810
	21st to end	Day	74% 6% 10% 7% 3	2573
January	1st to 10th	Night	59% 6% 13% 15% 5% 1	4428
	11th to 20th	Night	67% 9% 11% 10% 3	4404
	21st to end	Night	69% 5% 9% 14% 3	4532
February	1st to 10th	Night	62% 7% 9% 14% 7% 1	2470
	11th to 20th	Night	56% 6% 11% 17% 9% 1	2309
	21st to end	Night	55% 6% 12% 18% 8% 1	1884
March	1st to 10th	Night	53% 5% 12% 23% 7%	3614
	11th to 20th	Night	39% 7% 16% 19% 17% 1	3480
	21st to end	Night	47% 5% 12% 23% 13% 1	3817
April	1st to 10th	Night	48% 5% 12% 20% 13% 2	2024
	11th to 20th	Night	45% 6% 12% 18% 17% 2	1690
	21st to end	Night	43% 7% 11% 20% 16% 4	1710
May	1st to 10th	Night	45% 6% 11% 20% 14% 4	2840
	11th to 20th	Night	42% 7% 12% 25% 12% 2	2813
	21st to end	Night	32% 8% 12% 21% 20% 7%	3055
June	1st to 10th	Night	35% 6% 11% 28% 17% 2	1381
	11th to 20th	Night	35% 8% 14% 23% 19% 2	1330
	21st to end	Night	34% 6% 11% 26% 21% 1	1340
July	1st to 10th	Night	28% 5% 13% 31% 15% 6%	2490
	11th to 20th	Night	28% 6% 13% 34% 17% 1	2482
	21st to end	Night	29% 9% 18% 21% 21% 3	2979
August	1st to 10th	Night	35% 7% 14% 27% 17% 1	2814
	11th to 20th	Night	34% 7% 13% 32% 12% 2	2812
	21st to end	Night	34% 7% 12% 31% 15% 1	3124
September	1st to 10th	Night	35% 7% 13% 27% 16% 2	2012
	11th to 20th	Night	29% 7% 14% 30% 20% 1	2090
	21st to end	Night	40% 7% 11% 29% 12% 1	2090
October	1st to 10th	Night	27% 4 10% 32% 27% 1	3626
	11th to 20th	Night	43% 5% 11% 23% 17% 1	3779
	21st to end	Night	41% 5% 14% 25% 13% 1	4327
November	1st to 10th	Night	41% 6% 12% 26% 13% 1	2470
	11th to 20th	Night	50% 6% 14% 20% 9% 1	2470
	21st to end	Night	55% 6% 14% 18% 6%	2655
December	1st to 10th	Night	61% 9% 12% 14% 5%	2660
	11th to 20th	Night	56% 7% 14% 14% 8%	3382
	21st to end	Night	74% 6% 10% 7% 3	5076

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	22% 14% 37% 19% 7% 1	270
	11th to 20th	Day	21% 13% 44% 18% 4 1	270
	21st to end	Day	31% 6% 35% 22% 5% 1	297
February	1st to 10th	Day	20% 16% 39% 20% 4 1	270
	11th to 20th	Day	20% 15% 39% 24% 2	270
	21st to end	Day	18% 19% 44% 16% 3	225
March	1st to 10th	Day	20% 16% 37% 23% 4 1	336
	11th to 20th	Day	18% 13% 33% 28% 7% 2	460
	21st to end	Day	25% 10% 30% 27% 7% 1	506
April	1st to 10th	Day	13% 12% 38% 26% 9% 1	460
	11th to 20th	Day	25% 11% 28% 21% 11% 5%	452
	21st to end	Day	23% 8% 28% 28% 11% 2	460
May	1st to 10th	Day	21% 7% 28% 29% 13% 3	463
	11th to 20th	Day	18% 5% 24% 29% 18% 6%	487
	21st to end	Day	14% 3 19% 31% 23% 9%	529
June	1st to 10th	Day	11% 5% 25% 37% 17% 5%	625
	11th to 20th	Day	10% 4 25% 35% 22% 4	680
	21st to end	Day	11% 5% 25% 34% 20% 5%	680
July	1st to 10th	Day	8% 3 17% 32% 26% 13%	671
	11th to 20th	Day	10% 3 21% 35% 22% 9%	668
	21st to end	Day	8% 4 15% 35% 27% 11%	538
August	1st to 10th	Day	9% 2 15% 31% 28% 15%	486
	11th to 20th	Day	10% 3 12% 35% 27% 12%	479
	21st to end	Day	12% 4 17% 30% 24% 13%	539
September	1st to 10th	Day	11% 3 24% 23% 27% 12%	490
	11th to 20th	Day	8% 3 17% 23% 33% 17%	490
	21st to end	Day	16% 7% 23% 24% 20% 9%	490
October	1st to 10th	Day	14% 7% 28% 23% 18% 10%	490
	11th to 20th	Day	21% 13% 30% 25% 9% 3	490
	21st to end	Day	23% 13% 33% 22% 8% 1	416
November	1st to 10th	Day	16% 13% 33% 26% 12% 1	282
	11th to 20th	Day	19% 20% 31% 21% 8% 1	270
	21st to end	Day	26% 14% 34% 21% 4	180
December	1st to 10th	Day	21% 16% 39% 14% 8% 1	180
	11th to 20th	Day	26% 14% 41% 16% 4 1	180
	21st to end	Day	25% 14% 38% 20% 5%	240
January	1st to 10th	Night	23% 10% 37% 22% 6% 1	950
	11th to 20th	Night	25% 11% 34% 25% 4 1	927
	21st to end	Night	21% 7% 36% 29% 7%	836
February	1st to 10th	Night	21% 8% 41% 26% 4	760
	11th to 20th	Night	20% 10% 34% 30% 5%	743
	21st to end	Night	24% 10% 39% 24% 3	628
March	1st to 10th	Night	20% 9% 36% 29% 6%	760
	11th to 20th	Night	16% 11% 39% 27% 7% 1	760
	21st to end	Night	23% 7% 31% 29% 9% 1	836
April	1st to 10th	Night	20% 9% 34% 31% 5%	694
	11th to 20th	Night	21% 8% 32% 26% 10% 2	563
	21st to end	Night	19% 5% 32% 34% 9%	570
May	1st to 10th	Night	17% 4 28% 37% 12% 1	570
	11th to 20th	Night	19% 4 26% 33% 18% 1	561
	21st to end	Night	10% 3 20% 40% 25% 3	598
June	1st to 10th	Night	12% 3 24% 43% 18%	380
	11th to 20th	Night	10% 3 22% 46% 17% 1	380
	21st to end	Night	11% 2 19% 45% 23% 1	390
July	1st to 10th	Night	8% 2 14% 41% 30% 5%	555
	11th to 20th	Night	9% 2 16% 40% 28% 5%	552
	21st to end	Night	6% 2 16% 45% 28% 3	624
August	1st to 10th	Night	9% 2 14% 37% 35% 3	567
	11th to 20th	Night	6% 1 16% 38% 33% 5%	564
	21st to end	Night	9% 2 16% 38% 32% 4	627
September	1st to 10th	Night	11% 4 18% 34% 27% 6%	708
	11th to 20th	Night	10% 3 16% 34% 32% 6%	760
	21st to end	Night	17% 5% 19% 34% 20% 5%	760
October	1st to 10th	Night	15% 6% 26% 31% 19% 3	760
	11th to 20th	Night	22% 11% 27% 29% 9% 2	760
	21st to end	Night	25% 10% 32% 28% 6%	836
November	1st to 10th	Night	16% 10% 31% 28% 14% 1	760
	11th to 20th	Night	20% 13% 36% 23% 8% 1	760
	21st to end	Night	26% 12% 34% 22% 6%	760
December	1st to 10th	Night	26% 11% 36% 21% 6% 1	760
	11th to 20th	Night	22% 11% 38% 24% 4	817
	21st to end	Night	29% 11% 33% 24% 3	1045

Page generated at 2024-11-03 02:11:20. Version ac07

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