Providence
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Providence clear sky chart from 2005-11-06 to 2024-02-25.

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	17% 6% 2 5% 5% 3 4 5% 5% 7% 40%	78301
	Night	17% 7% 3 5% 5% 3 4 4 5% 6% 41%	80988
Transparency	Day	43% 6% 11% 22% 15% 3	78006
	Night	44% 5% 11% 22% 15% 2	80817
Seeing	Day	24% 18% 32% 18% 7% 2	14114
	Night	22% 14% 33% 23% 6% 1	23191

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	14% 7% 2 6% 4 3 4 4 5% 5% 46%	2517
	11th to 20th	Day	17% 7% 3 7% 5% 3 4 5% 4 5% 40%	2520
	21st to end	Day	21% 12% 3 5% 5% 3 3 4 4 5% 35%	2772
February	1st to 10th	Day	19% 7% 2 5% 4 3 6% 5% 5% 6% 38%	1809
	11th to 20th	Day	14% 7% 3 4 5% 3 5% 5% 5% 7% 43%	1848
	21st to end	Day	21% 8% 3 5% 4 3 4 5% 4 6% 38%	1520
March	1st to 10th	Day	16% 8% 2 5% 4 3 4 4 5% 7% 42%	1797
	11th to 20th	Day	17% 6% 2 4 5% 3 4 5% 6% 8% 40%	1894
	21st to end	Day	19% 8% 3 6% 4 3 4 4 4 5% 41%	2298
April	1st to 10th	Day	19% 7% 3 5% 4 3 3 5% 5% 7% 39%	2160
	11th to 20th	Day	18% 6% 3 5% 4 2 5% 4 6% 7% 41%	2134
	21st to end	Day	22% 6% 2 6% 5% 3 3 5% 4 6% 38%	2339
May	1st to 10th	Day	25% 8% 3 5% 4 3 4 4 5% 6% 33%	2340
	11th to 20th	Day	19% 6% 2 4 5% 3 4 4 5% 6% 41%	2313
	21st to end	Day	14% 6% 2 5% 5% 3 5% 4 5% 7% 44%	2725
June	1st to 10th	Day	19% 6% 3 5% 5% 3 5% 5% 7% 9% 34%	2520
	11th to 20th	Day	17% 6% 3 5% 5% 3 5% 5% 6% 9% 36%	2520
	21st to end	Day	15% 6% 2 5% 5% 3 5% 5% 7% 9% 37%	2520
July	1st to 10th	Day	13% 6% 2 5% 5% 3 6% 6% 6% 8% 40%	2520
	11th to 20th	Day	14% 5% 3 6% 6% 3 6% 6% 7% 10% 36%	2520
	21st to end	Day	13% 5% 2 6% 6% 4 6% 6% 6% 9% 37%	2744
August	1st to 10th	Day	11% 6% 3 6% 6% 4 5% 6% 7% 8% 38%	2339
	11th to 20th	Day	13% 5% 3 7% 5% 4 6% 6% 6% 7% 38%	2254
	21st to end	Day	12% 5% 3 6% 5% 3 5% 6% 5% 8% 42%	2376
September	1st to 10th	Day	15% 6% 2 5% 5% 3 4 5% 5% 6% 44%	2156
	11th to 20th	Day	14% 6% 2 4 3 3 4 3 4 6% 51%	1980
	21st to end	Day	18% 6% 2 4 4 2 4 4 4 6% 45%	1980
October	1st to 10th	Day	24% 6% 2 5% 3 3 3 4 3 5% 42%	1980
	11th to 20th	Day	16% 5% 2 4 4 2 4 4 5% 6% 47%	1774
	21st to end	Day	19% 5% 2 5% 5% 3 4 4 5% 5% 42%	1782
November	1st to 10th	Day	17% 6% 2 4 4 3 3 4 4 6% 48%	1671
	11th to 20th	Day	19% 6% 2 3 4 2 4 4 5% 7% 45%	1710
	21st to end	Day	17% 6% 2 5% 4 3 4 4 4 6% 46%	1710
December	1st to 10th	Day	19% 7% 3 5% 5% 2 4 4 4 7% 39%	1581
	11th to 20th	Day	21% 6% 2 5% 4 2 3 4 3 6% 46%	1906
	21st to end	Day	20% 9% 3 7% 5% 3 4 3 5% 6% 35%	2772
January	1st to 10th	Night	17% 7% 2 4 3 2 3 4 3 5% 49%	4429
	11th to 20th	Night	16% 10% 4 7% 5% 3 4 3 3 4 41%	4440
	21st to end	Night	22% 11% 4 7% 6% 3 4 4 4 4 31%	4884
February	1st to 10th	Night	17% 8% 3 6% 5% 3 3 4 5% 6% 41%	2364
	11th to 20th	Night	16% 7% 4 6% 5% 2 4 4 5% 5% 41%	2218
	21st to end	Night	17% 8% 3 6% 5% 2 5% 4 4 4 42%	1831
March	1st to 10th	Night	16% 7% 2 4 5% 3 4 4 5% 7% 43%	2150
	11th to 20th	Night	15% 8% 3 5% 5% 3 5% 4 5% 7% 39%	2065
	21st to end	Night	18% 9% 3 4 5% 3 3 4 4 5% 41%	2056
April	1st to 10th	Night	18% 8% 3 5% 5% 3 5% 4 5% 6% 39%	1800
	11th to 20th	Night	18% 7% 3 5% 4 3 4 5% 5% 6% 39%	1775
	21st to end	Night	21% 7% 3 6% 5% 2 3 3 3 6% 40%	1620
May	1st to 10th	Night	23% 9% 4 6% 5% 3 5% 4 4 6% 32%	1620
	11th to 20th	Night	20% 5% 3 6% 6% 3 4 4 6% 7% 37%	1593
	21st to end	Night	18% 7% 3 5% 6% 3 5% 4 5% 8% 37%	1551
June	1st to 10th	Night	17% 6% 3 7% 5% 3 4 4 6% 8% 37%	1440
	11th to 20th	Night	19% 5% 3 6% 6% 2 5% 3 5% 8% 38%	1440
	21st to end	Night	16% 6% 3 4 3 3 4 6% 6% 9% 39%	1440
July	1st to 10th	Night	12% 6% 3 5% 6% 3 5% 6% 7% 9% 39%	1440
	11th to 20th	Night	14% 7% 3 5% 5% 3 5% 7% 6% 10% 36%	1440
	21st to end	Night	13% 5% 3 6% 5% 3 6% 5% 6% 9% 39%	1574
August	1st to 10th	Night	9% 7% 4 5% 4 3 5% 5% 7% 9% 42%	1580
	11th to 20th	Night	10% 6% 3 5% 5% 4 6% 7% 6% 9% 39%	1642
	21st to end	Night	13% 6% 2 4 5% 2 3 5% 5% 7% 48%	1980
September	1st to 10th	Night	13% 5% 3 5% 6% 3 5% 5% 5% 6% 42%	1804
	11th to 20th	Night	15% 5% 2 4 4 2 3 3 4 6% 52%	1980
	21st to end	Night	17% 8% 2 6% 5% 2 4 4 4 6% 43%	1980
October	1st to 10th	Night	21% 7% 3 4 4 3 3 3 3 7% 42%	1980
	11th to 20th	Night	16% 5% 2 4 5% 2 4 4 5% 7% 46%	2182
	21st to end	Night	21% 7% 2 6% 5% 2 4 3 4 6% 39%	2574
November	1st to 10th	Night	15% 5% 2 5% 4 3 4 4 5% 5% 48%	2407
	11th to 20th	Night	18% 7% 2 5% 3 2 3 4 4 5% 46%	2470
	21st to end	Night	16% 5% 2 4 3 2 4 5% 4 7% 46%	2470
December	1st to 10th	Night	20% 8% 2 5% 4 3 4 4 4 6% 40%	2597
	11th to 20th	Night	19% 7% 3 4 4 2 4 4 5% 6% 43%	3288
	21st to end	Night	20% 11% 3 6% 5% 2 3 3 4 5% 36%	4884

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	41% 4 8% 30% 15% 2	2518
	11th to 20th	Day	46% 6% 9% 24% 13% 2	2520
	21st to end	Day	53% 5% 8% 22% 11% 2	2772
February	1st to 10th	Day	47% 6% 12% 18% 14% 3	1809
	11th to 20th	Day	42% 5% 10% 23% 16% 3	1857
	21st to end	Day	48% 4 10% 19% 15% 3	1520
March	1st to 10th	Day	42% 5% 12% 21% 15% 5%	1800
	11th to 20th	Day	42% 6% 9% 24% 15% 4	1894
	21st to end	Day	47% 5% 7% 17% 18% 6%	2298
April	1st to 10th	Day	46% 5% 10% 20% 17% 4	2160
	11th to 20th	Day	42% 6% 9% 22% 19% 3	2134
	21st to end	Day	47% 5% 9% 18% 16% 4	2339
May	1st to 10th	Day	51% 5% 9% 18% 14% 2	2340
	11th to 20th	Day	44% 6% 10% 18% 19% 3	2317
	21st to end	Day	39% 7% 15% 22% 14% 2	2725
June	1st to 10th	Day	46% 8% 12% 22% 11% 1	2520
	11th to 20th	Day	44% 8% 11% 22% 14% 2	2520
	21st to end	Day	42% 8% 13% 22% 14% 1	2520
July	1st to 10th	Day	40% 8% 11% 24% 15% 3	2450
	11th to 20th	Day	42% 7% 13% 24% 11% 2	2445
	21st to end	Day	39% 8% 13% 22% 14% 4	2591
August	1st to 10th	Day	40% 9% 15% 22% 13% 1	2325
	11th to 20th	Day	42% 8% 12% 23% 13% 1	2254
	21st to end	Day	39% 7% 11% 22% 19% 2	2376
September	1st to 10th	Day	40% 6% 11% 22% 20% 1	2156
	11th to 20th	Day	34% 5% 9% 24% 24% 3	1980
	21st to end	Day	41% 4 8% 21% 24% 2	1980
October	1st to 10th	Day	46% 5% 9% 20% 16% 3	1980
	11th to 20th	Day	38% 4 10% 30% 17% 2	1774
	21st to end	Day	44% 5% 13% 18% 16% 4	1782
November	1st to 10th	Day	40% 5% 12% 22% 19% 2	1671
	11th to 20th	Day	41% 4 10% 21% 21% 3	1710
	21st to end	Day	42% 4 12% 26% 13% 3	1710
December	1st to 10th	Day	47% 4 13% 17% 18% 2	1581
	11th to 20th	Day	44% 4 12% 17% 16% 6%	1906
	21st to end	Day	51% 5% 11% 21% 11% 1	2772
January	1st to 10th	Night	39% 3 11% 32% 12% 3	4429
	11th to 20th	Night	48% 4 11% 23% 11% 3	4440
	21st to end	Night	57% 5% 8% 17% 11% 2	4884
February	1st to 10th	Night	46% 5% 13% 21% 14% 2	2364
	11th to 20th	Night	46% 5% 9% 19% 17% 4	2220
	21st to end	Night	46% 4 7% 24% 15% 4	1831
March	1st to 10th	Night	41% 5% 9% 23% 16% 5%	2160
	11th to 20th	Night	45% 6% 10% 17% 18% 4	2066
	21st to end	Night	47% 4 8% 18% 18% 6%	2056
April	1st to 10th	Night	47% 5% 10% 19% 16% 3	1800
	11th to 20th	Night	45% 5% 9% 20% 18% 3	1775
	21st to end	Night	47% 6% 9% 19% 14% 5%	1620
May	1st to 10th	Night	54% 5% 10% 16% 12% 3	1620
	11th to 20th	Night	46% 6% 13% 19% 12% 4	1594
	21st to end	Night	47% 7% 17% 17% 12% 1	1552
June	1st to 10th	Night	47% 7% 12% 21% 12% 1	1440
	11th to 20th	Night	46% 6% 10% 23% 13% 1	1440
	21st to end	Night	40% 8% 15% 23% 13% 1	1440
July	1st to 10th	Night	41% 8% 13% 23% 14% 1	1400
	11th to 20th	Night	42% 7% 15% 27% 9% 1	1392
	21st to end	Night	40% 9% 13% 25% 11% 2	1486
August	1st to 10th	Night	38% 8% 15% 25% 12% 2	1570
	11th to 20th	Night	40% 9% 15% 24% 12% 1	1642
	21st to end	Night	35% 7% 11% 27% 19% 1	1980
September	1st to 10th	Night	41% 7% 10% 23% 17% 2	1804
	11th to 20th	Night	36% 5% 10% 22% 26% 2	1980
	21st to end	Night	44% 3 8% 21% 20% 3	1980
October	1st to 10th	Night	45% 5% 10% 21% 14% 4	1980
	11th to 20th	Night	38% 6% 12% 29% 15% 1	2182
	21st to end	Night	48% 5% 10% 20% 15% 2	2574
November	1st to 10th	Night	39% 5% 12% 22% 18% 4	2407
	11th to 20th	Night	42% 4 10% 22% 19% 3	2470
	21st to end	Night	38% 5% 12% 28% 14% 2	2470
December	1st to 10th	Night	47% 4 12% 21% 15% 1	2597
	11th to 20th	Night	43% 6% 14% 18% 18% 2	3288
	21st to end	Night	51% 5% 9% 24% 11% 1	4884

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	30% 26% 26% 15% 3	180
	11th to 20th	Day	27% 28% 34% 7% 3	180
	21st to end	Day	24% 26% 35% 12% 2 1	198
February	1st to 10th	Day	33% 23% 31% 12% 2	397
	11th to 20th	Day	30% 30% 31% 7% 2	456
	21st to end	Day	31% 22% 33% 11% 2	362
March	1st to 10th	Day	29% 21% 34% 13% 2	420
	11th to 20th	Day	29% 26% 30% 10% 4 1	420
	21st to end	Day	27% 24% 33% 9% 5% 2	462
April	1st to 10th	Day	33% 23% 26% 11% 5% 1	420
	11th to 20th	Day	27% 25% 30% 14% 3 1	412
	21st to end	Day	30% 21% 28% 17% 2 2	420
May	1st to 10th	Day	34% 22% 29% 12% 3	423
	11th to 20th	Day	24% 17% 40% 14% 4 1	447
	21st to end	Day	20% 16% 33% 23% 6% 2	485
June	1st to 10th	Day	23% 14% 34% 20% 8% 1	450
	11th to 20th	Day	17% 18% 38% 20% 5% 1	450
	21st to end	Day	19% 13% 37% 23% 7% 2	450
July	1st to 10th	Day	18% 10% 31% 28% 13% 2	445
	11th to 20th	Day	18% 6% 33% 29% 12% 3	444
	21st to end	Day	14% 10% 38% 27% 10% 1	488
August	1st to 10th	Day	13% 10% 33% 31% 10% 2	446
	11th to 20th	Day	15% 9% 32% 29% 12% 2	439
	21st to end	Day	13% 11% 34% 24% 13% 5%	495
September	1st to 10th	Day	20% 10% 28% 24% 14% 4	450
	11th to 20th	Day	18% 13% 28% 24% 10% 7%	450
	21st to end	Day	24% 12% 34% 19% 7% 4	450
October	1st to 10th	Day	29% 12% 27% 18% 9% 5%	450
	11th to 20th	Day	20% 16% 33% 18% 10% 2	405
	21st to end	Day	26% 19% 29% 17% 7% 2	396
November	1st to 10th	Day	22% 15% 33% 18% 9% 2	365
	11th to 20th	Day	27% 21% 31% 15% 6%	370
	21st to end	Day	25% 21% 30% 16% 7% 1	370
December	1st to 10th	Day	24% 28% 32% 10% 5%	241
	11th to 20th	Day	33% 25% 34% 6% 2	180
	21st to end	Day	27% 24% 32% 12% 3 2	198
January	1st to 10th	Night	23% 19% 37% 18% 3	760
	11th to 20th	Night	30% 19% 35% 14% 2	760
	21st to end	Night	22% 22% 35% 17% 3	836
February	1st to 10th	Night	24% 19% 37% 19% 1	760
	11th to 20th	Night	26% 22% 37% 13% 1	743
	21st to end	Night	25% 21% 34% 17% 3	611
March	1st to 10th	Night	24% 19% 37% 17% 3	720
	11th to 20th	Night	21% 22% 36% 17% 3	720
	21st to end	Night	26% 19% 34% 17% 4	792
April	1st to 10th	Night	25% 21% 33% 18% 3	720
	11th to 20th	Night	23% 18% 36% 19% 4	711
	21st to end	Night	26% 18% 36% 17% 3	540
May	1st to 10th	Night	30% 14% 32% 20% 4	540
	11th to 20th	Night	23% 16% 37% 21% 2	532
	21st to end	Night	22% 7% 35% 30% 6%	390
June	1st to 10th	Night	18% 8% 33% 31% 10%	360
	11th to 20th	Night	22% 6% 36% 29% 6%	360
	21st to end	Night	19% 3 36% 35% 6% 1	360
July	1st to 10th	Night	15% 4 33% 38% 10%	350
	11th to 20th	Night	15% 3 32% 39% 10% 1	348
	21st to end	Night	15% 3 31% 41% 9%	394
August	1st to 10th	Night	13% 4 35% 38% 10%	506
	11th to 20th	Night	13% 5% 29% 40% 12%	578
	21st to end	Night	15% 6% 25% 36% 15% 2	792
September	1st to 10th	Night	18% 5% 30% 35% 11% 1	720
	11th to 20th	Night	18% 7% 28% 28% 16% 2	720
	21st to end	Night	23% 7% 28% 28% 11% 2	720
October	1st to 10th	Night	26% 10% 26% 24% 11% 2	720
	11th to 20th	Night	20% 10% 35% 23% 12% 1	720
	21st to end	Night	25% 15% 32% 20% 7%	792
November	1st to 10th	Night	19% 14% 32% 24% 10% 1	740
	11th to 20th	Night	23% 17% 35% 18% 6%	760
	21st to end	Night	22% 20% 33% 21% 4 1	760
December	1st to 10th	Night	26% 17% 35% 17% 5%	760
	11th to 20th	Night	27% 19% 33% 19% 2	760
	21st to end	Night	27% 19% 35% 17% 2	836

Page generated at 2024-02-22 06:05:48. Version ac07

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