Monroe CAM
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monroe CAM 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	16% 7% 2 6% 4 4 4 4 5% 7% 40%	131005
	Night	16% 7% 2 6% 4 4 4 3 5% 6% 43%	130135
Transparency	Day	42% 5% 11% 23% 17% 3	134532
	Night	41% 4 11% 23% 17% 4	134695
Seeing	Day	23% 15% 30% 21% 9% 2	16640
	Night	20% 14% 31% 26% 8% 1	25961

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	13% 7% 2 6% 4 4 4 3 5% 5% 48%	4661
	11th to 20th	Day	16% 7% 3 6% 4 3 4 2 4 5% 46%	4650
	21st to end	Day	16% 8% 2 6% 5% 4 5% 4 5% 6% 41%	5720
February	1st to 10th	Day	15% 8% 2 7% 5% 4 4 3 5% 6% 41%	1890
	11th to 20th	Day	17% 9% 3 7% 4 4 4 3 4 6% 40%	2046
	21st to end	Day	18% 9% 3 7% 4 3 3 3 5% 5% 39%	1730
March	1st to 10th	Day	22% 6% 2 4 3 4 3 2 4 5% 44%	4496
	11th to 20th	Day	12% 7% 2 6% 5% 4 4 4 5% 7% 43%	4842
	21st to end	Day	18% 5% 2 6% 4 4 4 3 4 6% 43%	5876
April	1st to 10th	Day	18% 9% 3 6% 4 4 4 3 6% 6% 38%	2400
	11th to 20th	Day	16% 6% 2 6% 4 4 4 4 6% 9% 39%	2374
	21st to end	Day	17% 6% 2 6% 4 4 5% 4 6% 7% 40%	2400
May	1st to 10th	Day	26% 7% 3 6% 4 4 4 4 5% 8% 29%	5840
	11th to 20th	Day	24% 9% 2 6% 4 4 4 3 4 6% 34%	6304
	21st to end	Day	21% 6% 2 6% 4 4 5% 4 6% 8% 35%	6949
June	1st to 10th	Day	14% 6% 2 5% 4 5% 5% 5% 7% 9% 38%	2800
	11th to 20th	Day	15% 6% 2 7% 4 5% 6% 3 6% 8% 38%	2800
	21st to end	Day	11% 6% 3 6% 5% 5% 6% 4 6% 9% 40%	2800
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 6% 5% 7% 11% 36%	6360
	11th to 20th	Day	11% 7% 2 8% 5% 6% 6% 5% 8% 10% 31%	6360
	21st to end	Day	12% 7% 2 6% 4 5% 5% 4 6% 10% 39%	6926
August	1st to 10th	Day	19% 7% 2 7% 4 5% 5% 5% 7% 8% 31%	4216
	11th to 20th	Day	13% 6% 2 7% 4 5% 5% 4 6% 8% 40%	3850
	21st to end	Day	10% 6% 2 5% 4 4 4 4 6% 9% 47%	4312
September	1st to 10th	Day	13% 6% 3 7% 4 3 5% 2 5% 7% 45%	2400
	11th to 20th	Day	13% 5% 2 5% 4 3 3 3 5% 7% 49%	2330
	21st to end	Day	19% 7% 2 8% 4 4 5% 4 5% 6% 38%	2200
October	1st to 10th	Day	18% 7% 2 5% 3 4 4 3 5% 6% 44%	2061
	11th to 20th	Day	16% 6% 2 5% 3 3 3 3 4 6% 49%	2000
	21st to end	Day	18% 6% 2 5% 3 3 3 3 4 7% 47%	2076
November	1st to 10th	Day	12% 7% 2 5% 3 2 3 2 4 6% 51%	1851
	11th to 20th	Day	16% 6% 2 5% 3 3 4 3 6% 5% 47%	1890
	21st to end	Day	16% 6% 2 5% 4 3 3 3 5% 7% 45%	1801
December	1st to 10th	Day	14% 8% 3 6% 3 4 3 3 5% 7% 45%	2680
	11th to 20th	Day	20% 9% 2 4 3 3 4 2 4 5% 45%	3066
	21st to end	Day	17% 7% 2 6% 4 4 4 4 6% 7% 39%	4048
January	1st to 10th	Night	12% 8% 3 6% 4 3 3 3 5% 6% 48%	8234
	11th to 20th	Night	16% 8% 2 5% 3 3 3 3 4 6% 46%	8235
	21st to end	Night	16% 8% 2 5% 4 4 4 3 4 6% 44%	8443
February	1st to 10th	Night	16% 9% 3 6% 3 4 4 3 6% 6% 40%	2730
	11th to 20th	Night	18% 9% 3 6% 4 4 4 4 4 5% 40%	2458
	21st to end	Night	18% 8% 3 5% 4 3 3 4 5% 6% 41%	2076
March	1st to 10th	Night	19% 8% 2 6% 3 3 3 3 4 6% 44%	5389
	11th to 20th	Night	13% 9% 2 5% 4 3 4 3 4 5% 48%	5100
	21st to end	Night	18% 8% 2 6% 4 4 3 3 5% 5% 41%	5055
April	1st to 10th	Night	18% 7% 3 6% 4 4 4 4 6% 6% 39%	2000
	11th to 20th	Night	17% 7% 3 7% 4 3 4 3 5% 6% 40%	1975
	21st to end	Night	18% 6% 2 5% 3 3 4 4 5% 7% 44%	2000
May	1st to 10th	Night	23% 9% 4 7% 3 4 4 4 5% 8% 28%	4084
	11th to 20th	Night	23% 9% 3 7% 3 4 4 3 5% 6% 33%	3631
	21st to end	Night	22% 7% 3 5% 4 4 3 3 5% 9% 35%	3926
June	1st to 10th	Night	14% 7% 2 6% 4 4 4 5% 6% 8% 41%	1600
	11th to 20th	Night	12% 6% 2 6% 6% 4 4 5% 6% 8% 40%	1600
	21st to end	Night	10% 5% 2 7% 5% 5% 5% 5% 7% 10% 40%	1600
July	1st to 10th	Night	9% 5% 3 8% 6% 6% 6% 4 7% 10% 38%	3600
	11th to 20th	Night	12% 8% 3 8% 4 5% 5% 5% 7% 10% 33%	3600
	21st to end	Night	12% 6% 3 5% 4 4 5% 4 6% 8% 44%	3926
August	1st to 10th	Night	23% 7% 2 6% 4 4 4 4 7% 7% 32%	2896
	11th to 20th	Night	13% 6% 3 6% 5% 4 5% 4 6% 7% 42%	3197
	21st to end	Night	10% 5% 2 5% 4 4 4 3 5% 8% 51%	3586
September	1st to 10th	Night	14% 6% 3 7% 4 4 3 4 4 6% 45%	2000
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 7% 52%	2068
	21st to end	Night	19% 7% 3 6% 3 3 4 3 5% 7% 40%	2200
October	1st to 10th	Night	17% 6% 2 5% 4 3 3 3 5% 6% 45%	2335
	11th to 20th	Night	15% 5% 2 5% 4 4 3 3 4 6% 50%	2400
	21st to end	Night	18% 6% 3 5% 3 3 3 3 5% 5% 47%	2762
November	1st to 10th	Night	11% 5% 2 5% 4 3 3 3 5% 6% 53%	2667
	11th to 20th	Night	17% 6% 2 6% 4 3 3 3 4 5% 48%	2730
	21st to end	Night	13% 7% 2 5% 4 4 4 3 5% 6% 45%	2814
December	1st to 10th	Night	13% 8% 2 5% 3 3 3 3 5% 6% 47%	4720
	11th to 20th	Night	23% 7% 2 5% 3 3 3 3 4 5% 42%	5348
	21st to end	Night	19% 8% 3 6% 4 3 4 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% 3 9% 28% 19% 2	4662
	11th to 20th	Day	42% 3 7% 23% 20% 6%	4680
	21st to end	Day	44% 4 11% 24% 16% 1	5720
February	1st to 10th	Day	45% 3 11% 25% 14% 2	1890
	11th to 20th	Day	47% 4 7% 24% 15% 3	2055
	21st to end	Day	48% 3 8% 23% 14% 4	1730
March	1st to 10th	Day	42% 4 9% 22% 15% 8%	4499
	11th to 20th	Day	38% 6% 9% 27% 14% 5%	4842
	21st to end	Day	43% 4 9% 15% 24% 6%	5876
April	1st to 10th	Day	46% 5% 9% 19% 16% 5%	2400
	11th to 20th	Day	40% 6% 12% 22% 17% 3	2374
	21st to end	Day	42% 5% 9% 20% 19% 4	2400
May	1st to 10th	Day	53% 6% 13% 16% 10% 1	5851
	11th to 20th	Day	52% 4 9% 22% 13% 1	6308
	21st to end	Day	46% 6% 9% 23% 14% 2	6949
June	1st to 10th	Day	41% 6% 12% 23% 16% 2	2800
	11th to 20th	Day	43% 7% 12% 23% 12% 3	2800
	21st to end	Day	39% 6% 13% 23% 17% 1	2800
July	1st to 10th	Day	41% 9% 14% 21% 14% 1	6290
	11th to 20th	Day	45% 9% 17% 18% 10% 1	6285
	21st to end	Day	40% 7% 10% 21% 21% 1	6728
August	1st to 10th	Day	48% 7% 12% 22% 10% 1	4202
	11th to 20th	Day	40% 7% 13% 26% 13% 1	3886
	21st to end	Day	33% 6% 11% 26% 21% 2	4312
September	1st to 10th	Day	39% 5% 11% 21% 21% 3	2400
	11th to 20th	Day	34% 5% 9% 25% 24% 3	2330
	21st to end	Day	47% 5% 9% 17% 20% 3	2200
October	1st to 10th	Day	36% 5% 10% 19% 25% 5%	3360
	11th to 20th	Day	26% 2 10% 25% 31% 6%	3240
	21st to end	Day	27% 3 13% 26% 28% 4	3327
November	1st to 10th	Day	35% 3 11% 26% 22% 3	1851
	11th to 20th	Day	38% 4 8% 25% 22% 3	1890
	21st to end	Day	39% 3 12% 30% 13% 2	1801
December	1st to 10th	Day	40% 3 14% 27% 14% 1	2680
	11th to 20th	Day	44% 3 10% 28% 13% 2	3066
	21st to end	Day	42% 6% 10% 23% 17% 1	4048
January	1st to 10th	Night	38% 3 12% 25% 18% 5%	8234
	11th to 20th	Night	40% 3 10% 23% 18% 7%	8280
	21st to end	Night	42% 4 8% 23% 20% 3	8443
February	1st to 10th	Night	44% 3 13% 25% 13% 2	2730
	11th to 20th	Night	46% 3 8% 20% 18% 5%	2460
	21st to end	Night	43% 4 7% 24% 18% 4	2076
March	1st to 10th	Night	42% 3 8% 24% 13% 9%	5399
	11th to 20th	Night	39% 5% 13% 24% 15% 4	5101
	21st to end	Night	45% 4 6% 16% 23% 6%	5055
April	1st to 10th	Night	45% 4 9% 20% 18% 5%	2000
	11th to 20th	Night	44% 4 9% 19% 21% 3	1975
	21st to end	Night	40% 4 10% 20% 21% 5%	2000
May	1st to 10th	Night	53% 6% 11% 16% 10% 2	4090
	11th to 20th	Night	51% 6% 11% 17% 14% 2	3632
	21st to end	Night	46% 6% 12% 22% 12% 2	3927
June	1st to 10th	Night	40% 7% 11% 21% 20% 2	1600
	11th to 20th	Night	41% 7% 13% 26% 12% 1	1600
	21st to end	Night	38% 7% 15% 23% 16% 2	1600
July	1st to 10th	Night	42% 8% 15% 21% 12% 1	3560
	11th to 20th	Night	44% 9% 16% 21% 9% 1	3552
	21st to end	Night	37% 6% 15% 22% 18% 1	3809
August	1st to 10th	Night	48% 8% 17% 17% 9% 1	2886
	11th to 20th	Night	40% 6% 11% 30% 11% 1	3227
	21st to end	Night	31% 5% 11% 30% 21% 2	3586
September	1st to 10th	Night	40% 5% 10% 23% 19% 2	2000
	11th to 20th	Night	33% 5% 10% 23% 26% 4	2068
	21st to end	Night	44% 5% 7% 23% 20% 2	2200
October	1st to 10th	Night	37% 5% 11% 24% 22% 2	3816
	11th to 20th	Night	25% 3 9% 28% 30% 5%	3899
	21st to end	Night	27% 4 10% 31% 25% 3	4461
November	1st to 10th	Night	33% 3 11% 25% 23% 4	2667
	11th to 20th	Night	40% 3 8% 24% 20% 5%	2730
	21st to end	Night	39% 3 12% 27% 17% 2	2814
December	1st to 10th	Night	39% 3 11% 31% 14% 2	4720
	11th to 20th	Night	45% 3 10% 24% 14% 4	5348
	21st to end	Night	45% 4 9% 21% 18% 3	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	31% 24% 31% 12% 1 1	220
	11th to 20th	Day	40% 26% 24% 9% 1	220
	21st to end	Day	30% 27% 29% 10% 3	352
February	1st to 10th	Day	28% 28% 32% 10% 2	330
	11th to 20th	Day	34% 23% 32% 9% 1	534
	21st to end	Day	29% 24% 32% 12% 2	446
March	1st to 10th	Day	31% 22% 30% 14% 3	508
	11th to 20th	Day	26% 24% 32% 13% 4 1	500
	21st to end	Day	30% 24% 31% 11% 4 1	550
April	1st to 10th	Day	30% 26% 28% 10% 5% 1	500
	11th to 20th	Day	27% 18% 35% 13% 4 2	492
	21st to end	Day	30% 20% 30% 14% 5% 2	500
May	1st to 10th	Day	33% 15% 31% 13% 6% 1	503
	11th to 20th	Day	24% 16% 35% 18% 6% 1	527
	21st to end	Day	23% 11% 24% 28% 12% 2	573
June	1st to 10th	Day	18% 12% 31% 27% 10% 2	530
	11th to 20th	Day	21% 11% 33% 24% 9% 2	530
	21st to end	Day	15% 10% 33% 29% 11% 1	530
July	1st to 10th	Day	13% 6% 29% 30% 17% 6%	525
	11th to 20th	Day	9% 5% 26% 36% 20% 4	524
	21st to end	Day	15% 7% 30% 33% 13% 3	576
August	1st to 10th	Day	13% 7% 27% 32% 15% 5%	526
	11th to 20th	Day	14% 5% 25% 34% 18% 4	519
	21st to end	Day	14% 6% 31% 30% 13% 7%	583
September	1st to 10th	Day	16% 10% 30% 23% 15% 6%	530
	11th to 20th	Day	14% 8% 29% 29% 12% 8%	530
	21st to end	Day	24% 11% 30% 23% 8% 5%	530
October	1st to 10th	Day	25% 8% 26% 22% 13% 7%	530
	11th to 20th	Day	20% 17% 29% 23% 8% 3	530
	21st to end	Day	22% 17% 32% 17% 11% 2	514
November	1st to 10th	Day	19% 16% 35% 18% 9% 2	425
	11th to 20th	Day	26% 18% 32% 19% 5%	430
	21st to end	Day	26% 18% 35% 14% 6% 1	341
December	1st to 10th	Day	28% 27% 29% 10% 5%	220
	11th to 20th	Day	40% 19% 29% 9% 4	220
	21st to end	Day	33% 14% 31% 15% 5% 1	242
January	1st to 10th	Night	21% 24% 35% 16% 4	840
	11th to 20th	Night	25% 21% 31% 20% 3	840
	21st to end	Night	21% 24% 34% 19% 2	924
February	1st to 10th	Night	22% 20% 35% 21% 2	840
	11th to 20th	Night	26% 25% 35% 13% 1	823
	21st to end	Night	25% 22% 35% 16% 2	692
March	1st to 10th	Night	24% 22% 32% 18% 3	809
	11th to 20th	Night	24% 21% 33% 17% 4	800
	21st to end	Night	22% 16% 40% 17% 4	880
April	1st to 10th	Night	23% 23% 34% 18% 4	800
	11th to 20th	Night	22% 17% 38% 19% 4	791
	21st to end	Night	22% 15% 37% 22% 4	800
May	1st to 10th	Night	25% 16% 32% 22% 5%	617
	11th to 20th	Night	23% 10% 38% 24% 5%	424
	21st to end	Night	18% 7% 28% 35% 10% 2	433
June	1st to 10th	Night	17% 7% 31% 37% 9% 1	400
	11th to 20th	Night	14% 7% 30% 39% 11%	400
	21st to end	Night	11% 4 30% 44% 11%	400
July	1st to 10th	Night	12% 5% 25% 42% 15% 1	390
	11th to 20th	Night	10% 4 23% 44% 19% 1	388
	21st to end	Night	11% 2 30% 43% 14%	438
August	1st to 10th	Night	15% 2 21% 42% 19% 2	578
	11th to 20th	Night	13% 4 19% 41% 20% 2	790
	21st to end	Night	15% 3 21% 39% 20% 2	880
September	1st to 10th	Night	16% 4 28% 34% 16% 2	800
	11th to 20th	Night	16% 4 22% 33% 21% 4	800
	21st to end	Night	22% 6% 24% 32% 15% 1	800
October	1st to 10th	Night	21% 8% 26% 28% 15% 3	800
	11th to 20th	Night	18% 14% 28% 30% 10%	800
	21st to end	Night	23% 12% 34% 23% 8%	880
November	1st to 10th	Night	16% 12% 35% 25% 10% 1	820
	11th to 20th	Night	21% 19% 31% 22% 7%	840
	21st to end	Night	19% 19% 33% 22% 7%	840
December	1st to 10th	Night	26% 18% 31% 17% 6% 1	840
	11th to 20th	Night	23% 19% 34% 20% 4	840
	21st to end	Night	24% 19% 32% 23% 3	924

Page generated at 2026-02-28 01:40:22. Version ac07

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