Warren
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Warren clear sky chart from 2005-11-06 to 2024-08-30.

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% 12% 4 9% 5% 4 4 3 5% 7% 28%	95672
	Night	18% 14% 5% 10% 5% 4 4 3 4 6% 27%	93361
Transparency	Day	55% 6% 11% 18% 9% 1	95401
	Night	58% 5% 10% 17% 9% 1	93185
Seeing	Day	26% 17% 28% 17% 9% 3	14354
	Night	25% 15% 27% 22% 10% 1	23831

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	16% 25% 12% 15% 6% 4 3 2 3 3 13%	2563
	11th to 20th	Day	13% 22% 10% 18% 8% 4 3 1 3 3 15%	2840
	21st to end	Day	24% 18% 11% 16% 7% 4 4 2 3 2 9%	3124
February	1st to 10th	Day	18% 20% 6% 14% 9% 6% 4 2 2 4 16%	1710
	11th to 20th	Day	15% 16% 7% 17% 6% 5% 4 4 4 4 17%	1663
	21st to end	Day	20% 16% 4 13% 7% 4 3 4 4 5% 22%	1517
March	1st to 10th	Day	21% 12% 7% 8% 5% 4 3 3 4 6% 27%	3432
	11th to 20th	Day	11% 21% 7% 11% 4 3 3 3 4 5% 27%	3480
	21st to end	Day	20% 12% 4 12% 5% 3 3 3 4 6% 28%	3815
April	1st to 10th	Day	17% 17% 4 8% 4 4 4 3 5% 6% 28%	2242
	11th to 20th	Day	20% 13% 3 6% 4 4 4 3 5% 6% 31%	2259
	21st to end	Day	21% 12% 3 7% 4 4 3 3 4 5% 33%	2470
May	1st to 10th	Day	25% 9% 3 7% 5% 4 4 3 4 6% 29%	4108
	11th to 20th	Day	19% 10% 3 9% 5% 5% 5% 4 6% 7% 25%	4260
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 5% 8% 40%	4837
June	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	2660
	11th to 20th	Day	15% 7% 2 7% 5% 5% 6% 4 7% 9% 32%	2660
	21st to end	Day	18% 7% 2 5% 5% 5% 5% 4 6% 9% 35%	2660
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 6% 5% 7% 11% 36%	4440
	11th to 20th	Day	13% 7% 3 7% 5% 5% 6% 5% 7% 10% 34%	4320
	21st to end	Day	11% 7% 2 7% 5% 5% 6% 5% 6% 8% 37%	4466
August	1st to 10th	Day	13% 6% 2 8% 5% 6% 6% 5% 7% 10% 33%	2457
	11th to 20th	Day	15% 7% 2 8% 5% 6% 6% 5% 7% 9% 28%	2433
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 4 7% 9% 34%	2548
September	1st to 10th	Day	20% 8% 2 6% 4 4 4 3 5% 6% 37%	2160
	11th to 20th	Day	15% 6% 2 7% 4 5% 5% 3 6% 9% 37%	2062
	21st to end	Day	19% 7% 4 9% 5% 4 5% 3 6% 7% 31%	1936
October	1st to 10th	Day	20% 8% 3 6% 5% 5% 5% 4 6% 6% 32%	1800
	11th to 20th	Day	23% 11% 3 7% 5% 5% 4 3 5% 6% 28%	1800
	21st to end	Day	26% 15% 3 8% 5% 4 4 3 4 5% 23%	1980
November	1st to 10th	Day	15% 15% 4 7% 5% 4 4 3 5% 7% 31%	1732
	11th to 20th	Day	18% 19% 5% 9% 4 3 4 3 5% 6% 22%	1520
	21st to end	Day	21% 22% 6% 8% 5% 4 3 3 4 6% 18%	1520
December	1st to 10th	Day	19% 27% 10% 12% 4 3 3 3 3 4 12%	1520
	11th to 20th	Day	17% 21% 9% 14% 4 4 4 3 4 4 16%	1906
	21st to end	Day	24% 25% 8% 10% 5% 4 4 2 3 3 12%	2772
January	1st to 10th	Night	16% 23% 11% 17% 6% 4 3 2 3 4 11%	4367
	11th to 20th	Night	14% 20% 10% 19% 7% 6% 4 3 3 4 10%	4120
	21st to end	Night	25% 20% 8% 17% 7% 4 2 2 2 3 11%	4532
February	1st to 10th	Night	18% 20% 6% 13% 8% 5% 3 3 3 3 18%	2470
	11th to 20th	Night	15% 16% 7% 16% 8% 5% 5% 3 4 4 17%	2403
	21st to end	Night	20% 14% 5% 15% 6% 4 3 3 4 4 21%	1930
March	1st to 10th	Night	21% 16% 4 10% 5% 4 3 2 3 5% 28%	3408
	11th to 20th	Night	18% 18% 8% 9% 4 3 3 3 4 5% 26%	3479
	21st to end	Night	16% 13% 5% 10% 5% 3 3 3 4 5% 33%	3817
April	1st to 10th	Night	18% 16% 4 7% 4 3 4 3 5% 6% 29%	1936
	11th to 20th	Night	20% 13% 3 5% 4 4 3 4 4 6% 35%	1875
	21st to end	Night	16% 12% 3 7% 4 5% 4 3 5% 8% 33%	1722
May	1st to 10th	Night	27% 10% 3 6% 4 3 4 3 5% 6% 30%	2833
	11th to 20th	Night	18% 11% 3 8% 4 4 4 4 4 6% 33%	2630
	21st to end	Night	14% 7% 2 6% 3 3 4 4 6% 9% 41%	2738
June	1st to 10th	Night	14% 7% 2 7% 5% 5% 3 5% 7% 8% 38%	1520
	11th to 20th	Night	13% 8% 2 6% 5% 4 4 4 6% 10% 39%	1520
	21st to end	Night	15% 7% 2 6% 4 4 4 3 5% 9% 40%	1520
July	1st to 10th	Night	14% 8% 3 7% 5% 4 4 3 6% 7% 39%	2520
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 6% 8% 43%	2637
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 6% 8% 42%	3087
August	1st to 10th	Night	9% 6% 2 6% 5% 5% 5% 4 7% 9% 42%	1701
	11th to 20th	Night	15% 5% 2 6% 5% 4 4 4 7% 8% 39%	1688
	21st to end	Night	12% 6% 1 6% 4 4 4 5% 6% 10% 44%	1999
September	1st to 10th	Night	15% 8% 2 6% 4 4 4 3 5% 7% 43%	1800
	11th to 20th	Night	13% 6% 2 5% 4 3 3 4 5% 7% 47%	1894
	21st to end	Night	17% 9% 4 7% 4 4 5% 3 5% 7% 35%	2024
October	1st to 10th	Night	18% 7% 2 6% 5% 4 5% 3 5% 7% 38%	2160
	11th to 20th	Night	22% 10% 3 7% 4 3 4 3 6% 6% 31%	2160
	21st to end	Night	28% 12% 2 7% 4 4 4 3 4 5% 27%	2376
November	1st to 10th	Night	15% 14% 3 7% 3 3 3 4 5% 7% 36%	2343
	11th to 20th	Night	18% 18% 4 8% 4 4 5% 3 5% 6% 24%	2660
	21st to end	Night	19% 19% 6% 10% 5% 4 4 2 5% 6% 20%	2660
December	1st to 10th	Night	21% 26% 8% 10% 5% 4 4 2 3 3 13%	2660
	11th to 20th	Night	19% 21% 8% 15% 6% 4 3 2 3 3 15%	3288
	21st to end	Night	25% 23% 8% 11% 6% 4 4 3 4 4 9%	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	78% 4 7% 9% 3	2564
	11th to 20th	Day	77% 2 7% 11% 3	2840
	21st to end	Day	82% 4 6% 5% 2 1	3124
February	1st to 10th	Day	75% 3 7% 10% 4	1710
	11th to 20th	Day	70% 4 7% 13% 5%	1672
	21st to end	Day	64% 5% 10% 14% 5% 2	1517
March	1st to 10th	Day	59% 4 9% 23% 5%	3435
	11th to 20th	Day	59% 5% 15% 16% 5% 1	3480
	21st to end	Day	57% 5% 7% 20% 10% 1	3815
April	1st to 10th	Day	57% 4 10% 16% 11% 1	2242
	11th to 20th	Day	54% 6% 9% 19% 11% 2	2259
	21st to end	Day	54% 5% 9% 18% 12% 2	2470
May	1st to 10th	Day	56% 5% 8% 22% 8% 1	4120
	11th to 20th	Day	54% 8% 12% 18% 7% 1	4264
	21st to end	Day	40% 7% 12% 23% 15% 3	4837
June	1st to 10th	Day	48% 7% 12% 20% 13% 1	2660
	11th to 20th	Day	46% 9% 13% 21% 11% 1	2660
	21st to end	Day	45% 6% 13% 23% 12%	2660
July	1st to 10th	Day	40% 8% 13% 24% 14% 1	4370
	11th to 20th	Day	41% 7% 12% 22% 16%	4245
	21st to end	Day	42% 8% 13% 22% 14% 1	4324
August	1st to 10th	Day	44% 8% 14% 24% 9%	2444
	11th to 20th	Day	48% 10% 15% 19% 7% 1	2433
	21st to end	Day	44% 8% 13% 22% 12% 2	2548
September	1st to 10th	Day	48% 6% 11% 20% 14% 1	2160
	11th to 20th	Day	43% 6% 12% 25% 13% 1	2062
	21st to end	Day	50% 7% 10% 21% 10% 1	1936
October	1st to 10th	Day	50% 7% 13% 16% 13% 1	1800
	11th to 20th	Day	57% 5% 12% 18% 7%	1800
	21st to end	Day	64% 5% 10% 13% 7% 1	1980
November	1st to 10th	Day	52% 7% 11% 15% 12% 2	1732
	11th to 20th	Day	61% 6% 11% 14% 6% 2	1520
	21st to end	Day	68% 4 11% 11% 4 1	1520
December	1st to 10th	Day	77% 3 9% 9% 2	1520
	11th to 20th	Day	72% 5% 9% 11% 3	1906
	21st to end	Day	79% 4 9% 7% 1	2772
January	1st to 10th	Night	78% 4 6% 9% 2	4367
	11th to 20th	Night	80% 3 8% 7% 2	4120
	21st to end	Night	81% 3 6% 7% 2	4532
February	1st to 10th	Night	72% 4 7% 12% 5%	2470
	11th to 20th	Night	71% 5% 8% 12% 4	2405
	21st to end	Night	68% 4 8% 13% 8% 1	1930
March	1st to 10th	Night	61% 4 9% 22% 4	3418
	11th to 20th	Night	60% 5% 12% 15% 7% 1	3480
	21st to end	Night	53% 4 8% 19% 14% 2	3817
April	1st to 10th	Night	56% 4 12% 17% 11% 1	1936
	11th to 20th	Night	50% 6% 12% 19% 12% 2	1875
	21st to end	Night	49% 6% 11% 20% 11% 2	1722
May	1st to 10th	Night	54% 5% 10% 18% 11% 2	2840
	11th to 20th	Night	50% 8% 13% 19% 9% 1	2631
	21st to end	Night	38% 8% 12% 24% 15% 5%	2739
June	1st to 10th	Night	42% 7% 13% 23% 14% 1	1520
	11th to 20th	Night	40% 7% 15% 22% 14% 2	1520
	21st to end	Night	40% 8% 13% 23% 14% 1	1520
July	1st to 10th	Night	45% 6% 10% 21% 16% 2	2480
	11th to 20th	Night	37% 5% 15% 27% 15% 1	2589
	21st to end	Night	39% 7% 13% 21% 20% 1	2988
August	1st to 10th	Night	37% 8% 14% 28% 12% 1	1690
	11th to 20th	Night	40% 8% 17% 25% 10% 1	1688
	21st to end	Night	35% 8% 16% 26% 13% 2	1999
September	1st to 10th	Night	41% 6% 13% 24% 13% 3	1800
	11th to 20th	Night	36% 6% 13% 26% 18% 1	1894
	21st to end	Night	49% 6% 13% 19% 13% 1	2024
October	1st to 10th	Night	45% 6% 13% 20% 14% 1	2160
	11th to 20th	Night	52% 6% 13% 17% 10% 1	2160
	21st to end	Night	60% 5% 11% 16% 8% 1	2376
November	1st to 10th	Night	48% 5% 12% 21% 11% 3	2343
	11th to 20th	Night	61% 5% 10% 15% 7% 3	2660
	21st to end	Night	66% 5% 10% 14% 3 1	2660
December	1st to 10th	Night	77% 4 7% 9% 3	2660
	11th to 20th	Night	74% 4 10% 10% 2	3288
	21st to end	Night	79% 5% 8% 7% 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	34% 27% 29% 8% 3	195
	11th to 20th	Day	37% 31% 23% 6% 2	270
	21st to end	Day	34% 28% 28% 8% 1	297
February	1st to 10th	Day	35% 28% 29% 8%	270
	11th to 20th	Day	40% 28% 27% 5%	270
	21st to end	Day	43% 25% 27% 6%	282
March	1st to 10th	Day	32% 25% 30% 11% 2	460
	11th to 20th	Day	34% 20% 33% 9% 2 2	460
	21st to end	Day	37% 22% 24% 13% 4 1	506
April	1st to 10th	Day	31% 25% 26% 14% 4 1	460
	11th to 20th	Day	33% 22% 23% 12% 8% 2	452
	21st to end	Day	30% 19% 33% 14% 3 1	460
May	1st to 10th	Day	31% 21% 25% 14% 7% 2	463
	11th to 20th	Day	25% 15% 30% 20% 8% 2	487
	21st to end	Day	17% 13% 29% 22% 14% 4	529
June	1st to 10th	Day	23% 15% 28% 23% 9% 2	490
	11th to 20th	Day	19% 15% 28% 26% 12% 2	490
	21st to end	Day	20% 13% 36% 22% 7% 2	490
July	1st to 10th	Day	13% 10% 28% 24% 18% 7%	485
	11th to 20th	Day	15% 10% 29% 25% 16% 6%	484
	21st to end	Day	14% 12% 30% 26% 14% 5%	532
August	1st to 10th	Day	13% 10% 26% 25% 18% 7%	486
	11th to 20th	Day	18% 9% 25% 25% 14% 9%	479
	21st to end	Day	17% 8% 28% 25% 15% 8%	532
September	1st to 10th	Day	22% 12% 21% 23% 14% 7%	450
	11th to 20th	Day	16% 5% 25% 26% 20% 9%	450
	21st to end	Day	22% 14% 28% 18% 15% 4	450
October	1st to 10th	Day	21% 14% 30% 17% 14% 4	450
	11th to 20th	Day	30% 19% 30% 15% 5% 1	450
	21st to end	Day	38% 18% 27% 14% 3	495
November	1st to 10th	Day	28% 19% 28% 17% 6% 2	362
	11th to 20th	Day	41% 18% 28% 7% 5% 1	180
	21st to end	Day	36% 23% 32% 8% 1	180
December	1st to 10th	Day	38% 29% 22% 7% 2 2	180
	11th to 20th	Day	38% 26% 28% 7% 1	180
	21st to end	Day	40% 26% 28% 6% 1	198
January	1st to 10th	Night	31% 25% 32% 9% 3	760
	11th to 20th	Night	32% 25% 27% 14% 2	760
	21st to end	Night	28% 26% 30% 14% 2	836
February	1st to 10th	Night	34% 20% 31% 15%	760
	11th to 20th	Night	30% 27% 31% 11% 1	743
	21st to end	Night	32% 25% 27% 13% 2	628
March	1st to 10th	Night	29% 23% 30% 16% 3	760
	11th to 20th	Night	32% 21% 23% 18% 6%	760
	21st to end	Night	28% 19% 31% 17% 4 1	836
April	1st to 10th	Night	28% 17% 32% 19% 4	760
	11th to 20th	Night	28% 15% 29% 18% 8% 1	751
	21st to end	Night	23% 11% 34% 28% 4 1	582
May	1st to 10th	Night	26% 10% 25% 29% 11%	570
	11th to 20th	Night	20% 10% 30% 32% 8%	457
	21st to end	Night	15% 6% 29% 28% 20% 2	411
June	1st to 10th	Night	15% 4 31% 35% 14% 1	380
	11th to 20th	Night	14% 9% 27% 37% 12%	380
	21st to end	Night	16% 7% 30% 34% 13%	380
July	1st to 10th	Night	12% 4 22% 38% 20% 4	370
	11th to 20th	Night	12% 4 20% 39% 23% 2	433
	21st to end	Night	13% 5% 19% 39% 23% 1	624
August	1st to 10th	Night	12% 4 18% 37% 27% 2	567
	11th to 20th	Night	17% 4 17% 30% 29% 3	564
	21st to end	Night	14% 5% 20% 33% 26% 3	751
September	1st to 10th	Night	19% 6% 22% 29% 21% 3	720
	11th to 20th	Night	14% 7% 19% 30% 25% 4	720
	21st to end	Night	23% 11% 21% 25% 17% 4	720
October	1st to 10th	Night	22% 9% 25% 25% 17% 2	720
	11th to 20th	Night	28% 14% 29% 21% 7% 1	720
	21st to end	Night	36% 13% 29% 18% 3	792
November	1st to 10th	Night	23% 16% 29% 25% 8%	740
	11th to 20th	Night	31% 17% 30% 16% 5% 1	760
	21st to end	Night	31% 21% 28% 15% 4	760
December	1st to 10th	Night	37% 24% 25% 11% 3	760
	11th to 20th	Night	33% 24% 25% 14% 3	760
	21st to end	Night	32% 25% 28% 13% 1	836

Page generated at 2024-08-27 09:49:43. Version ac07

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