Monroe
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monroe clear sky chart from 2005-11-06 to 2026-03-03.

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% 7% 2 6% 4 4 4 4 5% 7% 39%	130769
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 42%	130406
Transparency	Day	42% 6% 12% 22% 16% 3	134297
	Night	42% 5% 11% 22% 17% 3	134965
Seeing	Day	21% 15% 31% 22% 9% 2	16618
	Night	21% 12% 31% 26% 8% 1	25800

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	11% 7% 3 7% 5% 5% 4 4 5% 5% 44%	4661
	11th to 20th	Day	16% 9% 2 6% 3 4 4 3 4 4 43%	4650
	21st to end	Day	15% 7% 3 7% 4 3 4 4 5% 6% 42%	5346
February	1st to 10th	Day	16% 8% 2 6% 5% 5% 5% 4 5% 6% 39%	1943
	11th to 20th	Day	15% 7% 2 5% 5% 3 5% 3 6% 7% 40%	2048
	21st to end	Day	21% 8% 2 6% 4 4 4 2 4 6% 39%	1730
March	1st to 10th	Day	23% 8% 2 5% 4 3 3 3 4 5% 41%	4496
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 5% 8% 42%	4674
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 6% 38%	5970
April	1st to 10th	Day	20% 9% 2 6% 4 4 4 4 5% 7% 36%	2400
	11th to 20th	Day	19% 7% 2 5% 4 4 4 4 5% 7% 40%	2374
	21st to end	Day	21% 6% 2 5% 4 4 4 3 5% 6% 41%	2488
May	1st to 10th	Day	31% 7% 2 5% 3 4 4 3 5% 8% 26%	5886
	11th to 20th	Day	22% 9% 3 6% 4 4 4 3 5% 6% 34%	6175
	21st to end	Day	22% 7% 2 6% 3 4 4 4 6% 8% 35%	6949
June	1st to 10th	Day	19% 6% 2 5% 5% 4 5% 4 8% 7% 36%	2800
	11th to 20th	Day	17% 6% 3 5% 5% 5% 5% 5% 7% 8% 35%	2800
	21st to end	Day	13% 7% 2 6% 5% 5% 4 4 6% 9% 38%	2800
July	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 7% 10% 34%	6360
	11th to 20th	Day	13% 7% 3 6% 5% 5% 5% 5% 8% 11% 34%	6360
	21st to end	Day	15% 6% 2 6% 4 5% 5% 4 6% 8% 39%	6926
August	1st to 10th	Day	20% 6% 3 7% 5% 4 4 4 6% 8% 32%	4387
	11th to 20th	Day	13% 6% 2 7% 4 4 4 4 6% 9% 42%	3850
	21st to end	Day	8% 5% 2 7% 4 5% 4 4 6% 10% 45%	4312
September	1st to 10th	Day	14% 6% 2 6% 5% 5% 4 3 5% 6% 44%	2400
	11th to 20th	Day	13% 5% 2 5% 4 3 4 3 5% 7% 50%	2275
	21st to end	Day	19% 6% 3 6% 5% 4 4 3 5% 7% 38%	2200
October	1st to 10th	Day	21% 6% 2 5% 4 3 3 3 5% 5% 44%	2147
	11th to 20th	Day	15% 5% 2 5% 3 4 4 4 5% 7% 46%	2000
	21st to end	Day	21% 5% 2 5% 4 4 4 3 5% 6% 42%	1984
November	1st to 10th	Day	13% 6% 2 6% 3 4 3 3 4 6% 50%	1851
	11th to 20th	Day	18% 6% 2 4 3 3 3 3 5% 7% 47%	1890
	21st to end	Day	18% 6% 2 5% 3 3 4 3 6% 7% 42%	1843
December	1st to 10th	Day	16% 7% 2 5% 4 4 3 3 5% 7% 44%	2680
	11th to 20th	Day	21% 7% 2 5% 3 3 3 3 4 6% 45%	3066
	21st to end	Day	18% 10% 4 7% 4 3 3 3 4 6% 38%	4048
January	1st to 10th	Night	14% 7% 2 5% 3 4 4 3 5% 7% 45%	8234
	11th to 20th	Night	15% 9% 3 7% 3 3 4 3 4 5% 44%	8235
	21st to end	Night	15% 8% 2 6% 4 4 4 3 4 6% 42%	8817
February	1st to 10th	Night	16% 9% 3 6% 4 4 4 3 5% 5% 41%	2674
	11th to 20th	Night	17% 9% 3 6% 4 4 3 3 5% 6% 40%	2458
	21st to end	Night	19% 8% 3 6% 5% 4 3 3 4 5% 41%	2076
March	1st to 10th	Night	20% 10% 2 5% 3 3 3 3 5% 5% 42%	5389
	11th to 20th	Night	15% 9% 3 5% 4 4 4 3 4 6% 43%	5283
	21st to end	Night	20% 10% 3 6% 3 3 3 2 4 5% 39%	4962
April	1st to 10th	Night	19% 8% 2 6% 4 4 4 4 5% 6% 37%	2000
	11th to 20th	Night	19% 7% 2 5% 4 4 3 3 5% 7% 39%	1975
	21st to end	Night	19% 7% 3 6% 4 3 3 3 4 6% 42%	1910
May	1st to 10th	Night	28% 11% 3 7% 4 4 3 3 4 6% 27%	4054
	11th to 20th	Night	22% 10% 3 7% 3 4 3 3 5% 7% 33%	3760
	21st to end	Night	23% 8% 3 6% 4 4 4 3 4 6% 36%	3926
June	1st to 10th	Night	18% 7% 2 6% 4 4 4 3 5% 6% 40%	1600
	11th to 20th	Night	17% 7% 2 6% 3 4 4 3 6% 8% 40%	1600
	21st to end	Night	13% 6% 2 5% 4 5% 4 3 6% 9% 42%	1600
July	1st to 10th	Night	15% 7% 3 7% 5% 4 5% 4 5% 9% 37%	3600
	11th to 20th	Night	18% 9% 3 7% 4 4 5% 3 6% 9% 32%	3600
	21st to end	Night	15% 6% 2 5% 4 4 4 4 6% 6% 44%	3926
August	1st to 10th	Night	23% 7% 2 7% 5% 5% 5% 4 6% 6% 31%	2726
	11th to 20th	Night	16% 6% 3 7% 5% 5% 4 3 5% 7% 40%	3197
	21st to end	Night	10% 5% 1 4 3 3 4 3 5% 7% 55%	3586
September	1st to 10th	Night	14% 6% 3 5% 4 4 3 3 4 7% 46%	2000
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 5% 6% 53%	2125
	21st to end	Night	19% 7% 2 5% 3 3 5% 3 4 5% 44%	2200
October	1st to 10th	Night	18% 7% 3 6% 4 3 3 3 4 7% 43%	2250
	11th to 20th	Night	16% 5% 2 6% 3 4 3 3 5% 6% 48%	2400
	21st to end	Night	22% 7% 2 5% 3 3 4 3 5% 5% 42%	2855
November	1st to 10th	Night	12% 6% 2 5% 3 4 4 3 5% 7% 49%	2667
	11th to 20th	Night	18% 7% 2 5% 3 3 3 3 5% 5% 48%	2730
	21st to end	Night	15% 6% 2 5% 4 4 4 3 5% 6% 46%	2773
December	1st to 10th	Night	17% 7% 2 5% 3 3 3 3 4 5% 49%	4720
	11th to 20th	Night	25% 7% 2 4 3 3 3 2 4 4 43%	5348
	21st to end	Night	19% 9% 3 6% 4 3 3 3 4 5% 41%	7150

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	39% 5% 10% 26% 17% 3	4662
	11th to 20th	Day	41% 4 10% 20% 16% 8%	4680
	21st to end	Day	40% 6% 10% 25% 18% 1	5346
February	1st to 10th	Day	45% 5% 11% 21% 15% 2	1943
	11th to 20th	Day	40% 5% 11% 23% 17% 3	2057
	21st to end	Day	45% 5% 12% 20% 14% 3	1730
March	1st to 10th	Day	46% 4 11% 17% 13% 10%	4499
	11th to 20th	Day	38% 5% 16% 27% 11% 2	4674
	21st to end	Day	46% 4 9% 14% 21% 6%	5970
April	1st to 10th	Day	46% 6% 10% 20% 15% 4	2400
	11th to 20th	Day	42% 6% 10% 20% 18% 3	2374
	21st to end	Day	44% 5% 10% 20% 17% 4	2488
May	1st to 10th	Day	54% 8% 15% 13% 9% 1	5897
	11th to 20th	Day	49% 6% 12% 18% 13% 2	6179
	21st to end	Day	45% 8% 11% 22% 13% 1	6949
June	1st to 10th	Day	43% 7% 12% 24% 13% 1	2800
	11th to 20th	Day	42% 8% 14% 23% 12% 1	2800
	21st to end	Day	40% 8% 14% 23% 14% 1	2800
July	1st to 10th	Day	45% 9% 11% 21% 13% 1	6290
	11th to 20th	Day	41% 8% 18% 22% 10% 1	6285
	21st to end	Day	41% 6% 11% 23% 18% 1	6728
August	1st to 10th	Day	47% 8% 15% 21% 9% 1	4373
	11th to 20th	Day	37% 7% 15% 30% 11% 1	3886
	21st to end	Day	33% 7% 14% 27% 17% 2	4312
September	1st to 10th	Day	39% 7% 11% 23% 19% 2	2400
	11th to 20th	Day	33% 6% 11% 24% 25% 2	2275
	21st to end	Day	44% 6% 10% 19% 18% 3	2200
October	1st to 10th	Day	35% 5% 10% 20% 24% 6%	3498
	11th to 20th	Day	28% 4 10% 24% 30% 5%	3240
	21st to end	Day	31% 4 14% 25% 23% 3	3184
November	1st to 10th	Day	37% 5% 13% 22% 22% 3	1851
	11th to 20th	Day	37% 4 11% 22% 22% 4	1890
	21st to end	Day	41% 4 13% 27% 12% 3	1843
December	1st to 10th	Day	39% 4 16% 28% 12% 1	2680
	11th to 20th	Day	41% 2 15% 19% 19% 3	3066
	21st to end	Day	48% 4 8% 21% 15% 4	4048
January	1st to 10th	Night	39% 4 11% 25% 19% 3	8234
	11th to 20th	Night	43% 4 11% 19% 17% 7%	8280
	21st to end	Night	44% 3 9% 20% 19% 4	8817
February	1st to 10th	Night	45% 5% 11% 23% 14% 2	2674
	11th to 20th	Night	44% 3 11% 20% 18% 4	2460
	21st to end	Night	46% 4 8% 23% 16% 4	2076
March	1st to 10th	Night	45% 3 11% 19% 15% 7%	5399
	11th to 20th	Night	43% 6% 14% 21% 12% 4	5284
	21st to end	Night	48% 4 7% 13% 24% 5%	4962
April	1st to 10th	Night	46% 6% 10% 19% 15% 4	2000
	11th to 20th	Night	44% 5% 11% 18% 21% 1	1975
	21st to end	Night	44% 4 9% 21% 17% 4	1910
May	1st to 10th	Night	58% 7% 13% 12% 10% 1	4060
	11th to 20th	Night	50% 7% 12% 15% 12% 3	3761
	21st to end	Night	50% 6% 13% 20% 10% 1	3927
June	1st to 10th	Night	45% 7% 10% 19% 18% 2	1600
	11th to 20th	Night	41% 8% 14% 25% 11% 1	1600
	21st to end	Night	39% 8% 13% 25% 14% 1	1600
July	1st to 10th	Night	45% 8% 13% 20% 12% 1	3560
	11th to 20th	Night	49% 7% 15% 19% 10% 1	3552
	21st to end	Night	39% 6% 13% 24% 17% 1	3809
August	1st to 10th	Night	52% 9% 12% 17% 9% 1	2716
	11th to 20th	Night	42% 7% 13% 29% 9% 1	3227
	21st to end	Night	28% 6% 13% 34% 18% 1	3586
September	1st to 10th	Night	39% 6% 9% 26% 18% 2	2000
	11th to 20th	Night	33% 6% 10% 23% 26% 3	2125
	21st to end	Night	43% 6% 8% 21% 19% 3	2200
October	1st to 10th	Night	38% 5% 11% 23% 20% 3	3679
	11th to 20th	Night	26% 4 9% 27% 29% 4	3899
	21st to end	Night	32% 4 13% 28% 20% 2	4605
November	1st to 10th	Night	35% 6% 12% 23% 21% 4	2667
	11th to 20th	Night	39% 3 9% 23% 20% 5%	2730
	21st to end	Night	39% 4 13% 29% 13% 2	2773
December	1st to 10th	Night	40% 3 12% 30% 14% 2	4720
	11th to 20th	Night	47% 3 11% 17% 18% 3	5348
	21st to end	Night	46% 3 11% 19% 16% 5%	7150

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	28% 27% 26% 17% 2	220
	11th to 20th	Day	23% 31% 32% 13% 1	220
	21st to end	Day	24% 26% 33% 11% 5% 1	283
February	1st to 10th	Day	26% 23% 37% 11% 2	383
	11th to 20th	Day	25% 24% 37% 12% 1	536
	21st to end	Day	28% 23% 31% 15% 3	446
March	1st to 10th	Day	23% 23% 35% 15% 4	508
	11th to 20th	Day	19% 25% 37% 15% 4 1	500
	21st to end	Day	26% 20% 38% 11% 4 1	550
April	1st to 10th	Day	26% 23% 31% 14% 5% 1	500
	11th to 20th	Day	27% 18% 33% 14% 6% 1	492
	21st to end	Day	27% 16% 35% 16% 4 1	500
May	1st to 10th	Day	31% 16% 31% 16% 5% 1	503
	11th to 20th	Day	23% 13% 35% 22% 7% 1	527
	21st to end	Day	20% 10% 29% 27% 11% 3	573
June	1st to 10th	Day	19% 10% 29% 25% 13% 2	530
	11th to 20th	Day	17% 10% 30% 29% 12% 1	530
	21st to end	Day	15% 8% 33% 30% 12% 2	530
July	1st to 10th	Day	17% 5% 30% 29% 17% 3	525
	11th to 20th	Day	12% 6% 27% 32% 19% 3	524
	21st to end	Day	14% 8% 30% 34% 13% 2	576
August	1st to 10th	Day	14% 6% 25% 36% 14% 6%	526
	11th to 20th	Day	15% 3 24% 35% 17% 6%	519
	21st to end	Day	10% 8% 30% 30% 16% 6%	583
September	1st to 10th	Day	18% 8% 27% 25% 18% 5%	530
	11th to 20th	Day	14% 6% 28% 30% 15% 8%	530
	21st to end	Day	21% 11% 29% 25% 10% 3	530
October	1st to 10th	Day	24% 10% 25% 21% 16% 5%	530
	11th to 20th	Day	18% 18% 28% 23% 10% 2	530
	21st to end	Day	25% 15% 31% 21% 8% 1	464
November	1st to 10th	Day	17% 16% 30% 23% 11% 2	425
	11th to 20th	Day	22% 25% 27% 20% 4	430
	21st to end	Day	26% 19% 30% 19% 5% 1	383
December	1st to 10th	Day	26% 18% 33% 18% 5%	220
	11th to 20th	Day	33% 25% 27% 13% 3	220
	21st to end	Day	24% 19% 34% 17% 5% 1	242
January	1st to 10th	Night	22% 20% 36% 19% 3	840
	11th to 20th	Night	27% 18% 32% 20% 3	840
	21st to end	Night	21% 19% 40% 18% 2	924
February	1st to 10th	Night	22% 17% 38% 21% 2	840
	11th to 20th	Night	25% 18% 38% 17% 2	823
	21st to end	Night	24% 20% 36% 17% 3	692
March	1st to 10th	Night	24% 18% 34% 21% 4	809
	11th to 20th	Night	23% 14% 37% 21% 4 1	800
	21st to end	Night	23% 17% 37% 19% 4	880
April	1st to 10th	Night	24% 17% 33% 22% 4	800
	11th to 20th	Night	24% 13% 35% 24% 4	791
	21st to end	Night	22% 13% 36% 23% 6% 1	710
May	1st to 10th	Night	28% 9% 33% 23% 6%	600
	11th to 20th	Night	24% 10% 36% 23% 7%	475
	21st to end	Night	23% 5% 22% 38% 11% 1	433
June	1st to 10th	Night	20% 4 28% 36% 11% 1	400
	11th to 20th	Night	18% 5% 27% 37% 14%	400
	21st to end	Night	14% 7% 21% 46% 13% 1	400
July	1st to 10th	Night	15% 4 23% 38% 19% 1	390
	11th to 20th	Night	16% 3 17% 42% 20% 2	388
	21st to end	Night	14% 3 22% 44% 14% 1	438
August	1st to 10th	Night	12% 1 25% 40% 21% 1	473
	11th to 20th	Night	16% 3 20% 38% 21% 2	790
	21st to end	Night	14% 4 24% 35% 21% 3	880
September	1st to 10th	Night	16% 4 27% 33% 18% 2	800
	11th to 20th	Night	17% 5% 21% 33% 19% 5%	800
	21st to end	Night	21% 8% 24% 31% 16% 1	800
October	1st to 10th	Night	22% 9% 27% 26% 14% 2	800
	11th to 20th	Night	20% 12% 31% 28% 10% 1	800
	21st to end	Night	26% 11% 35% 22% 7%	880
November	1st to 10th	Night	17% 13% 34% 25% 10% 1	820
	11th to 20th	Night	22% 17% 34% 20% 6% 1	840
	21st to end	Night	20% 17% 33% 25% 5% 1	840
December	1st to 10th	Night	26% 17% 31% 20% 5% 1	840
	11th to 20th	Night	25% 18% 32% 23% 3	840
	21st to end	Night	26% 18% 34% 19% 2	924

Page generated at 2026-02-28 01:40:20. Version ac07

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