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 2024-10-25.

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	18% 7% 2 6% 4 4 4 4 5% 7% 39%	101091
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 39%	97730
Transparency	Day	25% 49% 6% 11% 8% 1	100849
	Night	25% 49% 6% 11% 8% 1	97592
Seeing	Day	24% 18% 32% 18% 7% 2	15080
	Night	22% 14% 33% 23% 6% 1	23972

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 7% 4 4 4 3 5% 5% 46%	2517
	11th to 20th	Day	17% 8% 3 7% 4 4 5% 3 4 5% 40%	2520
	21st to end	Day	20% 12% 3 7% 4 3 3 3 5% 5% 35%	2772
February	1st to 10th	Day	19% 8% 2 5% 3 5% 5% 4 6% 6% 38%	1809
	11th to 20th	Day	14% 7% 2 5% 4 4 5% 4 5% 6% 43%	1848
	21st to end	Day	20% 8% 3 5% 3 4 4 4 5% 6% 37%	1570
March	1st to 10th	Day	25% 13% 3 6% 3 3 3 2 4 5% 32%	3116
	11th to 20th	Day	12% 5% 2 5% 4 5% 5% 4 6% 8% 45%	3338
	21st to end	Day	22% 10% 2 6% 4 4 4 4 5% 5% 36%	4032
April	1st to 10th	Day	19% 9% 3 6% 4 3 4 4 5% 6% 38%	2280
	11th to 20th	Day	18% 7% 3 5% 4 4 4 3 6% 7% 40%	2254
	21st to end	Day	22% 6% 2 7% 4 4 4 4 4 6% 38%	2469
May	1st to 10th	Day	27% 11% 3 7% 3 3 3 3 4 7% 29%	4106
	11th to 20th	Day	24% 9% 3 7% 5% 4 4 3 4 6% 32%	4107
	21st to end	Day	15% 5% 2 5% 4 4 4 3 5% 7% 45%	4837
June	1st to 10th	Day	18% 6% 2 6% 4 4 4 4 7% 9% 34%	2660
	11th to 20th	Day	16% 6% 2 6% 5% 4 5% 4 6% 9% 36%	2660
	21st to end	Day	15% 7% 2 6% 5% 4 5% 4 7% 9% 37%	2660
July	1st to 10th	Day	14% 6% 2 6% 5% 6% 6% 5% 8% 9% 34%	4440
	11th to 20th	Day	14% 6% 2 6% 4 5% 5% 5% 7% 10% 36%	4440
	21st to end	Day	19% 8% 2 7% 5% 5% 5% 4 6% 7% 32%	4814
August	1st to 10th	Day	17% 8% 3 8% 5% 5% 5% 4 6% 8% 30%	4117
	11th to 20th	Day	12% 6% 2 8% 5% 5% 6% 5% 6% 8% 38%	3953
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 7% 9% 45%	4180
September	1st to 10th	Day	15% 7% 2 5% 4 4 4 4 5% 6% 45%	2275
	11th to 20th	Day	13% 6% 2 5% 3 3 3 3 4 6% 51%	2090
	21st to end	Day	19% 7% 2 6% 4 3 5% 3 4 6% 43%	2090
October	1st to 10th	Day	23% 6% 1 5% 3 4 3 3 4 5% 42%	2090
	11th to 20th	Day	15% 5% 2 5% 3 3 4 3 5% 6% 49%	1872
	21st to end	Day	19% 5% 2 6% 4 4 3 4 5% 5% 43%	1825
November	1st to 10th	Day	17% 7% 2 5% 4 3 3 3 4 5% 48%	1671
	11th to 20th	Day	19% 6% 2 4 3 3 3 3 4 7% 45%	1710
	21st to end	Day	17% 7% 2 5% 4 3 4 3 4 6% 45%	1710
December	1st to 10th	Day	19% 8% 2 6% 4 3 4 3 4 7% 39%	1581
	11th to 20th	Day	20% 6% 2 6% 4 3 2 3 3 5% 46%	1906
	21st to end	Day	20% 9% 3 8% 4 4 4 2 5% 6% 35%	2772
January	1st to 10th	Night	17% 8% 2 5% 3 3 3 3 3 5% 49%	4429
	11th to 20th	Night	16% 10% 3 8% 4 4 3 3 4 4 41%	4440
	21st to end	Night	22% 12% 4 8% 5% 3 4 3 4 4 31%	4884
February	1st to 10th	Night	17% 8% 3 6% 5% 4 4 3 5% 6% 40%	2364
	11th to 20th	Night	16% 8% 3 6% 5% 4 3 4 5% 5% 41%	2218
	21st to end	Night	18% 9% 3 6% 4 3 4 3 4 4 42%	1884
March	1st to 10th	Night	29% 11% 2 4 3 3 3 3 4 5% 34%	3724
	11th to 20th	Night	10% 9% 3 6% 5% 4 4 3 6% 7% 43%	3621
	21st to end	Night	25% 8% 2 5% 4 4 4 4 5% 4 34%	3598
April	1st to 10th	Night	18% 9% 2 6% 5% 3 5% 3 5% 6% 37%	1900
	11th to 20th	Night	19% 8% 2 7% 4 4 4 4 5% 6% 38%	1875
	21st to end	Night	20% 7% 3 7% 4 3 3 3 4 6% 41%	1710
May	1st to 10th	Night	24% 10% 3 8% 5% 4 4 3 5% 7% 27%	2834
	11th to 20th	Night	24% 9% 3 8% 5% 5% 5% 3 6% 7% 26%	2813
	21st to end	Night	18% 6% 2 5% 5% 4 4 4 6% 7% 40%	2739
June	1st to 10th	Night	16% 7% 3 8% 4 4 4 3 6% 7% 37%	1520
	11th to 20th	Night	18% 6% 2 6% 5% 4 4 3 5% 8% 39%	1520
	21st to end	Night	16% 7% 2 5% 4 4 4 5% 7% 9% 38%	1520
July	1st to 10th	Night	15% 7% 3 6% 5% 4 6% 5% 7% 10% 33%	2520
	11th to 20th	Night	15% 8% 3 5% 4 3 5% 5% 6% 9% 37%	2520
	21st to end	Night	18% 9% 3 8% 5% 4 4 4 6% 7% 31%	2739
August	1st to 10th	Night	21% 7% 3 7% 5% 4 5% 4 7% 8% 29%	2780
	11th to 20th	Night	9% 7% 3 7% 5% 7% 6% 6% 6% 8% 35%	2870
	21st to end	Night	8% 5% 2 4 4 3 3 3 5% 8% 55%	3476
September	1st to 10th	Night	13% 5% 3 6% 5% 4 5% 4 5% 6% 43%	1905
	11th to 20th	Night	15% 6% 1 5% 3 3 3 3 4 6% 52%	2090
	21st to end	Night	18% 9% 2 6% 4 4 4 3 3 5% 41%	2090
October	1st to 10th	Night	20% 7% 3 5% 4 3 4 3 4 7% 41%	2090
	11th to 20th	Night	15% 5% 2 4 4 3 4 3 5% 7% 48%	2304
	21st to end	Night	20% 7% 2 6% 4 3 4 2 4 6% 40%	2637
November	1st to 10th	Night	15% 5% 2 5% 4 4 3 4 5% 5% 48%	2407
	11th to 20th	Night	18% 7% 2 5% 3 3 3 3 4 5% 46%	2470
	21st to end	Night	16% 6% 2 4 3 3 4 4 5% 7% 46%	2470
December	1st to 10th	Night	20% 8% 2 6% 4 4 3 3 4 5% 40%	2597
	11th to 20th	Night	19% 7% 2 5% 3 3 4 3 5% 6% 43%	3288
	21st to end	Night	20% 11% 3 7% 4 3 3 3 5% 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	26% 37% 5% 20% 10% 2	2518
	11th to 20th	Day	29% 39% 4 18% 8% 1	2520
	21st to end	Day	38% 41% 4 11% 5% 1	2772
February	1st to 10th	Day	17% 65% 6% 7% 4 1	1809
	11th to 20th	Day	17% 64% 2 7% 8% 2	1857
	21st to end	Day	15% 65% 4 9% 5% 1	1570
March	1st to 10th	Day	41% 41% 6% 6% 6% 2	3119
	11th to 20th	Day	18% 43% 10% 18% 10% 1	3338
	21st to end	Day	34% 40% 3 10% 8% 5%	4032
April	1st to 10th	Day	20% 65% 3 6% 5% 1	2280
	11th to 20th	Day	15% 66% 3 8% 8% 1	2254
	21st to end	Day	18% 65% 3 7% 6% 1	2469
May	1st to 10th	Day	37% 42% 9% 7% 5%	4120
	11th to 20th	Day	37% 41% 10% 8% 4	4111
	21st to end	Day	23% 42% 6% 15% 14% 1	4837
June	1st to 10th	Day	15% 65% 4 9% 6%	2660
	11th to 20th	Day	14% 65% 5% 10% 5% 1	2660
	21st to end	Day	14% 64% 4 9% 8%	2660
July	1st to 10th	Day	29% 40% 8% 13% 10% 1	4370
	11th to 20th	Day	27% 38% 11% 14% 9% 1	4365
	21st to end	Day	35% 37% 7% 11% 8% 1	4661
August	1st to 10th	Day	34% 40% 10% 12% 4	4103
	11th to 20th	Day	27% 40% 8% 20% 5%	3992
	21st to end	Day	16% 41% 10% 20% 12% 1	4180
September	1st to 10th	Day	15% 61% 4 11% 8%	2275
	11th to 20th	Day	16% 60% 4 9% 10% 2	2090
	21st to end	Day	19% 60% 3 9% 8% 1	2090
October	1st to 10th	Day	19% 60% 3 8% 7% 2	2090
	11th to 20th	Day	13% 60% 4 12% 11% 1	1872
	21st to end	Day	18% 60% 5% 8% 7% 2	1825
November	1st to 10th	Day	18% 59% 5% 9% 7% 1	1671
	11th to 20th	Day	16% 59% 4 8% 11% 2	1710
	21st to end	Day	15% 59% 4 13% 6% 2	1710
December	1st to 10th	Day	21% 60% 5% 5% 9%	1581
	11th to 20th	Day	23% 48% 6% 8% 9% 6%	1906
	21st to end	Day	34% 38% 6% 14% 7%	2772
January	1st to 10th	Night	23% 37% 7% 23% 7% 3	4429
	11th to 20th	Night	29% 37% 7% 16% 8% 2	4440
	21st to end	Night	42% 40% 5% 8% 5% 1	4884
February	1st to 10th	Night	17% 65% 5% 7% 5% 1	2364
	11th to 20th	Night	16% 64% 3 6% 10% 2	2220
	21st to end	Night	17% 64% 3 8% 6% 2	1884
March	1st to 10th	Night	38% 41% 5% 9% 6% 2	3734
	11th to 20th	Night	20% 42% 11% 13% 12% 2	3622
	21st to end	Night	36% 41% 3 6% 10% 4	3598
April	1st to 10th	Night	20% 65% 3 6% 5% 1	1900
	11th to 20th	Night	15% 66% 5% 6% 7% 1	1875
	21st to end	Night	17% 65% 3 7% 6% 1	1710
May	1st to 10th	Night	35% 45% 8% 10% 2	2840
	11th to 20th	Night	40% 42% 9% 7% 2	2814
	21st to end	Night	25% 42% 9% 15% 8%	2740
June	1st to 10th	Night	15% 65% 4 9% 7%	1520
	11th to 20th	Night	15% 65% 4 10% 6%	1520
	21st to end	Night	13% 64% 5% 11% 6% 1	1520
July	1st to 10th	Night	31% 40% 7% 12% 10%	2480
	11th to 20th	Night	28% 39% 11% 15% 8%	2472
	21st to end	Night	35% 38% 7% 10% 10% 1	2651
August	1st to 10th	Night	37% 40% 7% 9% 5% 1	2770
	11th to 20th	Night	28% 42% 8% 17% 4	2897
	21st to end	Night	13% 39% 11% 20% 16%	3476
September	1st to 10th	Night	16% 60% 4 12% 7% 1	1905
	11th to 20th	Night	16% 60% 3 9% 11% 1	2090
	21st to end	Night	21% 60% 3 8% 7%	2090
October	1st to 10th	Night	20% 60% 4 9% 4 3	2090
	11th to 20th	Night	11% 60% 5% 12% 10% 1	2304
	21st to end	Night	19% 61% 4 9% 6% 1	2637
November	1st to 10th	Night	18% 60% 5% 9% 8% 1	2407
	11th to 20th	Night	16% 59% 4 8% 10% 2	2470
	21st to end	Night	14% 60% 5% 13% 6% 2	2470
December	1st to 10th	Night	21% 60% 4 8% 7%	2597
	11th to 20th	Night	22% 49% 7% 9% 12% 2	3288
	21st to end	Night	34% 38% 5% 15% 7%	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% 21% 34% 11% 3	382
March	1st to 10th	Day	31% 20% 33% 13% 2	460
	11th to 20th	Day	30% 26% 29% 11% 4 1	460
	21st to end	Day	29% 23% 32% 8% 5% 2	506
April	1st to 10th	Day	33% 23% 26% 11% 5% 1	460
	11th to 20th	Day	29% 25% 30% 13% 3 1	452
	21st to end	Day	28% 21% 29% 17% 2 2	460
May	1st to 10th	Day	33% 23% 29% 12% 3	463
	11th to 20th	Day	24% 17% 40% 14% 3 1	487
	21st to end	Day	19% 16% 35% 22% 5% 2	529
June	1st to 10th	Day	23% 14% 33% 21% 8% 1	490
	11th to 20th	Day	16% 19% 37% 21% 6% 1	490
	21st to end	Day	19% 13% 38% 22% 7% 1	490
July	1st to 10th	Day	18% 11% 31% 27% 12% 1	485
	11th to 20th	Day	18% 8% 32% 29% 11% 3	484
	21st to end	Day	15% 11% 38% 26% 9% 1	532
August	1st to 10th	Day	14% 10% 34% 30% 9% 2	486
	11th to 20th	Day	15% 9% 33% 29% 11% 3	479
	21st to end	Day	12% 10% 35% 24% 13% 5%	539
September	1st to 10th	Day	19% 11% 29% 23% 13% 4	490
	11th to 20th	Day	18% 12% 27% 24% 12% 7%	490
	21st to end	Day	24% 11% 34% 19% 7% 4	490
October	1st to 10th	Day	28% 12% 27% 19% 9% 5%	490
	11th to 20th	Day	20% 17% 33% 18% 10% 3	440
	21st to end	Day	25% 18% 29% 17% 8% 2	411
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	26% 21% 33% 16% 3	628
March	1st to 10th	Night	25% 18% 36% 17% 4	760
	11th to 20th	Night	21% 23% 36% 17% 3	760
	21st to end	Night	27% 19% 34% 16% 4	836
April	1st to 10th	Night	25% 20% 34% 18% 3	760
	11th to 20th	Night	23% 19% 35% 18% 4	751
	21st to end	Night	25% 18% 37% 17% 3	570
May	1st to 10th	Night	29% 14% 31% 20% 4	570
	11th to 20th	Night	23% 16% 37% 22% 2	562
	21st to end	Night	21% 7% 36% 29% 6%	412
June	1st to 10th	Night	17% 10% 33% 31% 9%	380
	11th to 20th	Night	21% 6% 37% 29% 6%	380
	21st to end	Night	19% 4 36% 34% 6% 1	380
July	1st to 10th	Night	16% 4 33% 38% 9%	370
	11th to 20th	Night	15% 4 33% 38% 9% 1	368
	21st to end	Night	16% 4 30% 41% 9%	416
August	1st to 10th	Night	15% 5% 34% 37% 9%	535
	11th to 20th	Night	13% 5% 30% 39% 12%	611
	21st to end	Night	15% 6% 25% 37% 16% 2	836
September	1st to 10th	Night	18% 6% 31% 34% 11% 1	760
	11th to 20th	Night	18% 7% 28% 28% 17% 3	760
	21st to end	Night	25% 7% 28% 27% 11% 2	760
October	1st to 10th	Night	25% 10% 26% 25% 12% 2	760
	11th to 20th	Night	19% 11% 35% 23% 12% 1	760
	21st to end	Night	25% 15% 32% 21% 7%	812
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 2024-10-22 20:21:06. Version ac07

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