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 2024-12-02.

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%	101499
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 41%	98136
Transparency	Day	42% 6% 12% 22% 15% 2	105045
	Night	43% 5% 12% 22% 16% 2	102679
Seeing	Day	20% 14% 31% 23% 10% 2	15089
	Night	21% 12% 31% 26% 9% 1	24170

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	15% 7% 2 6% 4 4 3 3 4 4 46%	2517
	11th to 20th	Day	17% 9% 3 8% 4 5% 5% 4 5% 5% 35%	2520
	21st to end	Day	21% 11% 4 8% 5% 3 3 3 4 5% 31%	2882
February	1st to 10th	Day	18% 8% 2 5% 4 5% 4 4 5% 6% 38%	1757
	11th to 20th	Day	15% 7% 2 5% 4 3 4 4 6% 8% 42%	1848
	21st to end	Day	22% 8% 2 6% 4 4 4 3 4 6% 37%	1570
March	1st to 10th	Day	27% 9% 2 6% 4 4 3 3 3 4 35%	3116
	11th to 20th	Day	10% 5% 2 5% 4 5% 6% 5% 6% 8% 43%	3272
	21st to end	Day	21% 7% 2 6% 4 3 4 3 5% 5% 40%	4166
April	1st to 10th	Day	19% 9% 2 6% 4 3 3 4 5% 7% 36%	2280
	11th to 20th	Day	19% 7% 2 6% 4 4 4 4 5% 7% 40%	2254
	21st to end	Day	21% 6% 2 5% 4 4 4 3 5% 5% 40%	2363
May	1st to 10th	Day	29% 8% 2 5% 4 4 3 3 5% 7% 30%	4106
	11th to 20th	Day	22% 8% 3 7% 4 5% 4 4 6% 7% 31%	4297
	21st to end	Day	16% 5% 2 5% 3 3 4 4 6% 8% 44%	4837
June	1st to 10th	Day	19% 6% 2 5% 5% 4 5% 4 8% 7% 37%	2660
	11th to 20th	Day	16% 6% 2 5% 5% 5% 5% 5% 7% 9% 36%	2660
	21st to end	Day	13% 7% 2 6% 5% 5% 4 4 6% 9% 39%	2660
July	1st to 10th	Day	13% 6% 2 7% 5% 6% 5% 4 7% 10% 35%	4440
	11th to 20th	Day	14% 6% 2 5% 5% 5% 5% 5% 7% 10% 38%	4440
	21st to end	Day	17% 7% 3 8% 6% 5% 5% 4 6% 7% 32%	4814
August	1st to 10th	Day	20% 6% 3 8% 5% 4 4 4 7% 8% 31%	4252
	11th to 20th	Day	13% 6% 2 7% 4 4 4 4 6% 9% 42%	3730
	21st to end	Day	8% 5% 2 7% 4 5% 4 4 6% 10% 45%	4180
September	1st to 10th	Day	14% 6% 2 6% 5% 5% 4 3 5% 6% 44%	2280
	11th to 20th	Day	13% 5% 1 5% 4 3 4 3 5% 6% 49%	2161
	21st to end	Day	20% 6% 3 6% 5% 4 4 3 5% 7% 39%	2090
October	1st to 10th	Day	22% 6% 2 5% 5% 3 3 3 5% 5% 42%	2040
	11th to 20th	Day	15% 5% 2 5% 3 3 4 3 5% 6% 47%	1900
	21st to end	Day	22% 5% 2 5% 4 4 4 3 5% 6% 41%	1885
November	1st to 10th	Day	13% 6% 2 6% 3 4 3 3 4 6% 51%	1761
	11th to 20th	Day	18% 6% 2 4 3 3 3 3 5% 7% 47%	1800
	21st to end	Day	18% 6% 2 5% 3 3 4 3 6% 7% 43%	1755
December	1st to 10th	Day	19% 7% 3 6% 5% 4 4 4 6% 6% 37%	1528
	11th to 20th	Day	23% 6% 2 4 3 3 3 3 4 6% 44%	1906
	21st to end	Day	18% 11% 3 7% 5% 4 4 3 4 6% 32%	2772
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 5% 6% 45%	4429
	11th to 20th	Night	16% 10% 3 6% 4 3 4 3 5% 5% 42%	4440
	21st to end	Night	24% 12% 3 7% 4 4 3 3 3 5% 33%	4756
February	1st to 10th	Night	17% 9% 3 6% 4 4 4 3 5% 5% 41%	2420
	11th to 20th	Night	16% 9% 3 6% 4 4 3 3 5% 6% 41%	2218
	21st to end	Night	20% 7% 3 5% 5% 3 3 3 4 5% 41%	1884
March	1st to 10th	Night	24% 12% 2 5% 3 3 3 3 4 5% 34%	3724
	11th to 20th	Night	11% 7% 2 5% 5% 4 4 3 5% 7% 45%	3685
	21st to end	Night	20% 10% 3 5% 3 3 3 2 5% 5% 42%	3466
April	1st to 10th	Night	19% 8% 2 6% 4 4 4 4 6% 6% 37%	1900
	11th to 20th	Night	19% 7% 2 5% 4 4 3 3 5% 7% 40%	1875
	21st to end	Night	20% 7% 3 6% 4 3 3 3 4 5% 42%	1815
May	1st to 10th	Night	24% 10% 3 8% 4 4 4 3 4 6% 29%	2834
	11th to 20th	Night	23% 9% 3 8% 4 4 4 4 5% 7% 30%	2624
	21st to end	Night	18% 7% 2 5% 3 3 4 3 5% 7% 43%	2738
June	1st to 10th	Night	18% 7% 2 6% 4 4 4 3 5% 6% 40%	1520
	11th to 20th	Night	16% 7% 2 6% 3 4 4 4 6% 8% 41%	1520
	21st to end	Night	13% 6% 2 5% 4 5% 4 3 6% 10% 42%	1520
July	1st to 10th	Night	13% 6% 2 7% 6% 5% 6% 5% 6% 9% 36%	2520
	11th to 20th	Night	17% 7% 2 6% 4 5% 5% 3 7% 9% 35%	2520
	21st to end	Night	20% 7% 2 6% 4 4 5% 5% 6% 7% 34%	2739
August	1st to 10th	Night	23% 7% 2 7% 5% 5% 5% 4 6% 6% 30%	2642
	11th to 20th	Night	16% 6% 3 6% 5% 5% 4 3 5% 7% 40%	3097
	21st to end	Night	10% 5% 1 4 3 3 4 3 5% 7% 54%	3476
September	1st to 10th	Night	15% 6% 3 6% 4 4 3 3 4 7% 45%	1900
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 5% 6% 53%	2019
	21st to end	Night	19% 7% 2 6% 3 3 5% 3 4 5% 44%	2090
October	1st to 10th	Night	19% 7% 3 6% 4 3 3 3 4 7% 41%	2137
	11th to 20th	Night	15% 4 2 6% 3 4 4 3 5% 6% 48%	2280
	21st to end	Night	23% 7% 2 5% 3 4 4 3 4 5% 41%	2712
November	1st to 10th	Night	12% 6% 2 5% 3 4 3 3 5% 6% 50%	2537
	11th to 20th	Night	19% 7% 2 5% 3 3 3 3 4 5% 47%	2600
	21st to end	Night	16% 6% 2 5% 4 4 4 3 5% 6% 46%	2641
December	1st to 10th	Night	20% 7% 3 5% 3 4 4 3 5% 5% 41%	2686
	11th to 20th	Night	20% 7% 2 4 4 4 4 3 5% 6% 41%	3288
	21st to end	Night	21% 10% 3 6% 4 4 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	39% 4 11% 31% 13% 3	2518
	11th to 20th	Day	47% 5% 13% 23% 11% 1	2520
	21st to end	Day	51% 8% 8% 19% 11% 2	2882
February	1st to 10th	Day	45% 5% 12% 21% 14% 2	1757
	11th to 20th	Day	40% 5% 11% 24% 17% 3	1857
	21st to end	Day	47% 6% 11% 19% 13% 4	1570
March	1st to 10th	Day	53% 3 13% 18% 11% 2	3119
	11th to 20th	Day	32% 7% 17% 30% 13% 1	3272
	21st to end	Day	45% 3 8% 17% 21% 6%	4166
April	1st to 10th	Day	45% 6% 10% 20% 15% 4	2280
	11th to 20th	Day	42% 6% 10% 20% 18% 3	2254
	21st to end	Day	45% 5% 10% 20% 17% 4	2363
May	1st to 10th	Day	52% 8% 14% 14% 11% 1	4120
	11th to 20th	Day	49% 8% 14% 18% 10% 2	4301
	21st to end	Day	35% 8% 13% 25% 18% 2	4837
June	1st to 10th	Day	43% 7% 12% 24% 13% 1	2660
	11th to 20th	Day	41% 8% 14% 23% 12% 1	2660
	21st to end	Day	40% 8% 14% 23% 14% 1	2660
July	1st to 10th	Day	43% 10% 11% 21% 14% 1	4370
	11th to 20th	Day	39% 8% 17% 22% 13% 1	4365
	21st to end	Day	48% 8% 12% 16% 14% 1	4661
August	1st to 10th	Day	47% 8% 15% 21% 9%	4238
	11th to 20th	Day	37% 7% 14% 30% 11% 1	3766
	21st to end	Day	33% 7% 14% 27% 17% 2	4180
September	1st to 10th	Day	39% 7% 11% 22% 19% 2	2280
	11th to 20th	Day	34% 6% 11% 23% 24% 2	2161
	21st to end	Day	44% 6% 9% 20% 18% 3	2090
October	1st to 10th	Day	36% 6% 10% 20% 23% 6%	3391
	11th to 20th	Day	27% 4 10% 24% 30% 5%	3140
	21st to end	Day	32% 4 14% 25% 23% 3	3085
November	1st to 10th	Day	37% 5% 13% 22% 22% 3	1761
	11th to 20th	Day	37% 4 11% 21% 22% 4	1800
	21st to end	Day	40% 5% 14% 26% 13% 3	1755
December	1st to 10th	Day	45% 5% 16% 18% 14% 1	1528
	11th to 20th	Day	42% 3 16% 19% 18% 2	1906
	21st to end	Day	51% 5% 11% 22% 9% 1	2772
January	1st to 10th	Night	39% 4 11% 30% 12% 4	4429
	11th to 20th	Night	44% 5% 12% 23% 13% 3	4440
	21st to end	Night	54% 4 9% 20% 12% 2	4756
February	1st to 10th	Night	45% 5% 11% 23% 13% 2	2420
	11th to 20th	Night	44% 3 11% 19% 18% 5%	2220
	21st to end	Night	46% 4 8% 23% 16% 4	1884
March	1st to 10th	Night	52% 4 10% 20% 12% 2	3734
	11th to 20th	Night	37% 7% 15% 22% 16% 3	3686
	21st to end	Night	45% 4 8% 12% 25% 6%	3466
April	1st to 10th	Night	45% 6% 11% 19% 16% 3	1900
	11th to 20th	Night	44% 5% 11% 19% 20% 1	1875
	21st to end	Night	45% 4 9% 21% 16% 4	1815
May	1st to 10th	Night	55% 8% 11% 15% 10% 1	2840
	11th to 20th	Night	53% 9% 13% 14% 10% 1	2625
	21st to end	Night	42% 6% 14% 23% 13% 1	2739
June	1st to 10th	Night	45% 7% 10% 19% 18% 2	1520
	11th to 20th	Night	39% 8% 15% 26% 11% 1	1520
	21st to end	Night	39% 8% 13% 26% 14% 1	1520
July	1st to 10th	Night	43% 10% 14% 18% 13% 1	2480
	11th to 20th	Night	44% 7% 15% 22% 11% 1	2472
	21st to end	Night	49% 7% 13% 15% 15% 2	2651
August	1st to 10th	Night	52% 9% 13% 16% 9% 1	2632
	11th to 20th	Night	43% 7% 13% 28% 9% 1	3127
	21st to end	Night	28% 6% 13% 34% 18% 1	3476
September	1st to 10th	Night	40% 6% 9% 25% 18% 2	1900
	11th to 20th	Night	33% 6% 10% 23% 25% 3	2019
	21st to end	Night	43% 6% 7% 21% 20% 3	2090
October	1st to 10th	Night	38% 6% 11% 22% 20% 2	3566
	11th to 20th	Night	25% 5% 9% 27% 30% 4	3779
	21st to end	Night	32% 4 13% 28% 20% 3	4462
November	1st to 10th	Night	35% 6% 12% 22% 21% 4	2537
	11th to 20th	Night	40% 3 10% 23% 20% 4	2600
	21st to end	Night	39% 4 13% 29% 13% 2	2641
December	1st to 10th	Night	45% 5% 12% 22% 15% 1	2686
	11th to 20th	Night	44% 5% 13% 17% 18% 3	3288
	21st to end	Night	49% 4 13% 21% 12% 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	24% 28% 26% 21% 2	180
	11th to 20th	Day	19% 31% 34% 15% 1 1	180
	21st to end	Day	20% 24% 36% 13% 6% 1	231
February	1st to 10th	Day	26% 23% 36% 12% 2	317
	11th to 20th	Day	22% 25% 38% 13% 1	456
	21st to end	Day	29% 22% 30% 16% 3	382
March	1st to 10th	Day	21% 22% 37% 16% 4	460
	11th to 20th	Day	18% 25% 37% 15% 4 1	460
	21st to end	Day	24% 20% 39% 11% 5% 1	506
April	1st to 10th	Day	24% 22% 33% 15% 6% 1	460
	11th to 20th	Day	26% 17% 34% 15% 6% 2	452
	21st to end	Day	27% 17% 34% 16% 5% 1	460
May	1st to 10th	Day	30% 16% 31% 16% 5% 1	463
	11th to 20th	Day	22% 11% 37% 23% 7% 1	487
	21st to end	Day	18% 9% 29% 29% 12% 3	529
June	1st to 10th	Day	19% 10% 29% 26% 14% 3	490
	11th to 20th	Day	16% 9% 30% 30% 13% 1	490
	21st to end	Day	15% 8% 33% 29% 12% 3	490
July	1st to 10th	Day	16% 4 29% 29% 18% 4	485
	11th to 20th	Day	13% 5% 26% 32% 20% 3	484
	21st to end	Day	14% 7% 30% 34% 13% 2	532
August	1st to 10th	Day	15% 6% 23% 37% 14% 6%	486
	11th to 20th	Day	15% 3 24% 34% 18% 6%	479
	21st to end	Day	11% 6% 29% 31% 17% 6%	539
September	1st to 10th	Day	17% 8% 26% 26% 18% 5%	490
	11th to 20th	Day	14% 6% 28% 29% 15% 8%	490
	21st to end	Day	21% 12% 28% 25% 10% 3	490
October	1st to 10th	Day	25% 10% 25% 21% 15% 4	490
	11th to 20th	Day	17% 17% 30% 24% 10% 2	490
	21st to end	Day	25% 14% 31% 22% 8% 1	431
November	1st to 10th	Day	16% 15% 31% 24% 12% 3	395
	11th to 20th	Day	22% 24% 28% 21% 5% 1	400
	21st to end	Day	23% 18% 31% 21% 6% 1	355
December	1st to 10th	Day	23% 18% 35% 19% 6%	182
	11th to 20th	Day	30% 26% 28% 14% 3	180
	21st to end	Day	22% 20% 35% 18% 5% 1	198
January	1st to 10th	Night	21% 20% 36% 19% 4	760
	11th to 20th	Night	26% 18% 33% 20% 3	760
	21st to end	Night	21% 18% 39% 19% 3	836
February	1st to 10th	Night	22% 17% 37% 22% 2	760
	11th to 20th	Night	24% 18% 39% 17% 2	743
	21st to end	Night	24% 20% 35% 17% 4	628
March	1st to 10th	Night	23% 18% 34% 21% 4	760
	11th to 20th	Night	22% 14% 38% 21% 4 1	760
	21st to end	Night	22% 17% 37% 19% 4	836
April	1st to 10th	Night	23% 17% 33% 23% 4	760
	11th to 20th	Night	23% 13% 35% 25% 5%	751
	21st to end	Night	22% 12% 35% 24% 6% 1	675
May	1st to 10th	Night	27% 9% 33% 24% 7%	570
	11th to 20th	Night	23% 10% 37% 23% 7%	451
	21st to end	Night	22% 5% 21% 39% 11% 1	411
June	1st to 10th	Night	20% 4 28% 36% 11% 1	380
	11th to 20th	Night	18% 4 27% 37% 14%	380
	21st to end	Night	14% 6% 21% 46% 12% 1	380
July	1st to 10th	Night	15% 4 23% 38% 20% 1	370
	11th to 20th	Night	15% 2 17% 43% 20% 2	368
	21st to end	Night	15% 4 22% 43% 15% 1	416
August	1st to 10th	Night	12% 1 26% 40% 20% 1	449
	11th to 20th	Night	17% 3 20% 37% 21% 3	750
	21st to end	Night	14% 3 22% 35% 22% 3	836
September	1st to 10th	Night	16% 4 27% 33% 18% 3	760
	11th to 20th	Night	18% 5% 21% 32% 19% 5%	760
	21st to end	Night	21% 8% 24% 30% 16% 1	760
October	1st to 10th	Night	22% 9% 28% 26% 13% 3	760
	11th to 20th	Night	18% 11% 31% 29% 10% 1	760
	21st to end	Night	26% 11% 34% 22% 7%	836
November	1st to 10th	Night	15% 13% 34% 25% 11% 1	780
	11th to 20th	Night	22% 16% 35% 20% 6% 1	800
	21st to end	Night	20% 17% 33% 24% 5% 1	800
December	1st to 10th	Night	26% 16% 32% 20% 5% 1	768
	11th to 20th	Night	23% 18% 33% 23% 3	760
	21st to end	Night	26% 17% 36% 19% 2	836

Page generated at 2024-11-29 10:43:04. Version ac07

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