Mosquito Hill Nature Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mosquito Hill Nature Center clear sky chart from 2005-11-06 to 2025-12-03.

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	12% 8% 3 7% 5% 4 5% 4 6% 7% 38%	127245
	Night	13% 10% 3 8% 5% 4 4 3 5% 6% 39%	123734
Transparency	Day	43% 6% 12% 25% 13% 1	130708
	Night	44% 6% 12% 23% 14% 2	128332
Seeing	Day	16% 10% 29% 26% 14% 5%	17452
	Night	17% 9% 31% 31% 11% 1	27317

By Month

Percentage Cloud Cover SE (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	9% 9% 3 12% 6% 6% 5% 4 5% 6% 35%	3617
	11th to 20th	Day	8% 11% 4 10% 6% 6% 7% 5% 6% 7% 29%	3620
	21st to end	Day	11% 13% 6% 12% 6% 5% 3 3 4 5% 32%	3982
February	1st to 10th	Day	9% 12% 4 10% 5% 4 6% 4 7% 6% 32%	1795
	11th to 20th	Day	10% 11% 4 8% 6% 4 5% 3 6% 6% 37%	1884
	21st to end	Day	11% 12% 4 9% 6% 5% 5% 4 5% 7% 34%	1650
March	1st to 10th	Day	13% 7% 2 5% 3 3 4 3 5% 7% 47%	4480
	11th to 20th	Day	10% 7% 3 7% 4 4 4 4 7% 9% 41%	4697
	21st to end	Day	24% 11% 4 10% 4 4 4 3 4 5% 29%	5966
April	1st to 10th	Day	16% 12% 3 8% 5% 5% 5% 4 5% 7% 31%	2400
	11th to 20th	Day	20% 9% 3 6% 5% 5% 4 3 5% 6% 34%	2374
	21st to end	Day	19% 9% 3 8% 6% 5% 4 4 6% 5% 32%	2536
May	1st to 10th	Day	13% 6% 2 6% 4 3 4 3 5% 7% 44%	6085
	11th to 20th	Day	12% 6% 2 7% 4 4 5% 4 6% 8% 42%	6319
	21st to end	Day	15% 7% 2 6% 4 4 5% 4 6% 8% 38%	6935
June	1st to 10th	Day	11% 6% 2 7% 5% 4 4 4 6% 8% 42%	2800
	11th to 20th	Day	14% 7% 3 6% 4 4 5% 4 6% 9% 38%	2800
	21st to end	Day	11% 7% 2 7% 4 5% 5% 4 6% 9% 40%	2800
July	1st to 10th	Day	11% 5% 2 6% 4 5% 5% 5% 7% 10% 39%	6360
	11th to 20th	Day	6% 3 2 5% 4 4 5% 5% 8% 10% 48%	6360
	21st to end	Day	8% 6% 3 7% 5% 5% 5% 4 6% 8% 44%	6924
August	1st to 10th	Day	9% 6% 3 6% 4 5% 6% 4 7% 8% 42%	4563
	11th to 20th	Day	12% 5% 2 5% 4 4 4 4 6% 9% 45%	4041
	21st to end	Day	10% 6% 3 7% 5% 4 5% 4 6% 8% 41%	4312
September	1st to 10th	Day	11% 6% 3 6% 4 4 4 4 6% 9% 44%	2400
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 9% 47%	2310
	21st to end	Day	12% 7% 2 7% 5% 5% 4 4 6% 7% 41%	2200
October	1st to 10th	Day	13% 7% 3 5% 3 4 4 4 4 6% 45%	2075
	11th to 20th	Day	19% 9% 3 8% 5% 4 4 3 6% 7% 32%	1974
	21st to end	Day	16% 10% 3 8% 5% 4 3 3 4 7% 37%	1980
November	1st to 10th	Day	13% 7% 2 7% 4 4 5% 4 4 7% 42%	1852
	11th to 20th	Day	12% 12% 3 11% 6% 5% 5% 3 6% 7% 31%	1858
	21st to end	Day	15% 11% 4 8% 6% 4 4 4 5% 6% 34%	1680
December	1st to 10th	Day	8% 12% 4 10% 6% 7% 5% 5% 6% 6% 31%	2626
	11th to 20th	Day	12% 17% 5% 11% 5% 5% 4 3 4 5% 29%	3008
	21st to end	Day	20% 19% 7% 12% 6% 4 4 2 3 4 18%	3982
January	1st to 10th	Night	10% 12% 6% 10% 5% 4 4 3 4 5% 39%	6348
	11th to 20th	Night	10% 13% 5% 11% 6% 5% 6% 5% 7% 6% 26%	6360
	21st to end	Night	10% 15% 6% 11% 6% 5% 4 3 4 5% 31%	6996
February	1st to 10th	Night	10% 13% 5% 10% 5% 4 4 4 5% 5% 35%	2600
	11th to 20th	Night	10% 9% 4 9% 6% 5% 4 3 5% 5% 38%	2401
	21st to end	Night	15% 11% 4 8% 5% 5% 4 4 4 6% 36%	1980
March	1st to 10th	Night	14% 7% 2 5% 3 3 4 3 5% 7% 47%	5373
	11th to 20th	Night	9% 9% 3 8% 5% 5% 5% 3 6% 8% 39%	5307
	21st to end	Night	22% 10% 3 9% 5% 4 4 3 5% 5% 30%	4962
April	1st to 10th	Night	18% 11% 3 8% 4 3 4 3 4 6% 36%	2000
	11th to 20th	Night	21% 7% 2 6% 5% 4 3 4 5% 7% 36%	1975
	21st to end	Night	17% 8% 3 6% 5% 4 3 4 6% 6% 39%	1863
May	1st to 10th	Night	15% 7% 3 6% 4 4 4 4 5% 7% 41%	3817
	11th to 20th	Night	9% 5% 2 6% 4 4 5% 4 7% 8% 45%	3596
	21st to end	Night	19% 8% 2 6% 4 4 4 3 5% 6% 38%	3942
June	1st to 10th	Night	10% 4 2 7% 4 5% 5% 3 7% 7% 47%	1600
	11th to 20th	Night	12% 6% 3 8% 5% 4 4 4 6% 8% 41%	1600
	21st to end	Night	8% 6% 2 5% 5% 4 5% 4 6% 9% 46%	1600
July	1st to 10th	Night	11% 5% 2 6% 4 4 4 4 6% 8% 45%	3618
	11th to 20th	Night	8% 4 2 5% 3 3 4 4 6% 8% 53%	3617
	21st to end	Night	5% 5% 2 6% 4 5% 5% 4 6% 8% 50%	3947
August	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 6% 8% 47%	2597
	11th to 20th	Night	11% 6% 2 6% 4 4 5% 4 5% 7% 45%	3008
	21st to end	Night	9% 5% 2 6% 4 4 4 3 6% 7% 49%	3586
September	1st to 10th	Night	9% 5% 2 5% 3 4 4 3 5% 6% 54%	2000
	11th to 20th	Night	12% 5% 2 5% 3 2 5% 3 5% 6% 53%	2070
	21st to end	Night	11% 6% 2 5% 5% 4 4 4 6% 6% 48%	2200
October	1st to 10th	Night	12% 7% 2 6% 3 4 5% 3 5% 7% 48%	2320
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 4 5% 6% 37%	2425
	21st to end	Night	18% 10% 2 7% 5% 4 5% 4 5% 7% 34%	2860
November	1st to 10th	Night	14% 9% 3 6% 4 3 4 4 4 6% 44%	2666
	11th to 20th	Night	14% 10% 4 9% 5% 4 4 4 5% 7% 34%	2756
	21st to end	Night	15% 12% 2 7% 5% 4 4 4 5% 7% 36%	2940
December	1st to 10th	Night	9% 11% 4 8% 5% 4 4 4 5% 8% 38%	4609
	11th to 20th	Night	14% 18% 7% 11% 5% 4 3 3 4 4 28%	5199
	21st to end	Night	20% 17% 5% 11% 5% 4 4 3 4 5% 22%	6996

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	49% 5% 15% 20% 10% 1	3618
	11th to 20th	Day	52% 5% 10% 19% 13% 1	3620
	21st to end	Day	55% 4 10% 20% 11%	3982
February	1st to 10th	Day	50% 6% 12% 20% 11% 1	1795
	11th to 20th	Day	46% 5% 11% 24% 11% 2	1894
	21st to end	Day	49% 6% 13% 21% 10% 2	1650
March	1st to 10th	Day	37% 4 14% 23% 16% 6%	4480
	11th to 20th	Day	39% 5% 17% 23% 15% 2	4697
	21st to end	Day	59% 5% 7% 18% 11% 1	5968
April	1st to 10th	Day	52% 6% 11% 19% 11% 1	2400
	11th to 20th	Day	51% 5% 9% 21% 12% 2	2374
	21st to end	Day	52% 6% 11% 19% 11% 2	2536
May	1st to 10th	Day	38% 6% 12% 26% 16% 2	6120
	11th to 20th	Day	37% 7% 11% 28% 15% 1	6323
	21st to end	Day	42% 6% 10% 26% 15% 2	6949
June	1st to 10th	Day	38% 7% 12% 28% 15% 2	2800
	11th to 20th	Day	41% 7% 14% 24% 14% 1	2800
	21st to end	Day	38% 8% 14% 25% 14% 2	2800
July	1st to 10th	Day	37% 8% 13% 32% 9% 1	6291
	11th to 20th	Day	26% 8% 16% 34% 15% 1	6285
	21st to end	Day	36% 7% 12% 24% 19% 2	6728
August	1st to 10th	Day	37% 7% 16% 26% 13% 1	4548
	11th to 20th	Day	34% 7% 13% 34% 12%	4082
	21st to end	Day	38% 8% 13% 25% 15% 1	4311
September	1st to 10th	Day	37% 7% 14% 27% 15% 1	2400
	11th to 20th	Day	34% 7% 17% 31% 12% 1	2310
	21st to end	Day	41% 6% 13% 29% 11%	2200
October	1st to 10th	Day	25% 4 8% 38% 24% 1	3374
	11th to 20th	Day	43% 5% 9% 27% 15% 1	3190
	21st to end	Day	43% 5% 13% 29% 10%	3180
November	1st to 10th	Day	42% 6% 13% 23% 15% 1	1852
	11th to 20th	Day	52% 5% 13% 20% 9% 1	1858
	21st to end	Day	51% 5% 16% 20% 6% 1	1680
December	1st to 10th	Day	52% 7% 15% 21% 4 1	2626
	11th to 20th	Day	58% 4 11% 17% 10% 1	3005
	21st to end	Day	71% 5% 6% 12% 7%	3982
January	1st to 10th	Night	49% 4 9% 25% 12% 1	6348
	11th to 20th	Night	56% 6% 8% 14% 15% 1	6360
	21st to end	Night	55% 5% 12% 16% 11%	6996
February	1st to 10th	Night	51% 5% 10% 21% 11% 2	2600
	11th to 20th	Night	48% 4 10% 23% 12% 2	2402
	21st to end	Night	50% 5% 13% 20% 11% 2	1980
March	1st to 10th	Night	37% 4 15% 26% 13% 4	5373
	11th to 20th	Night	42% 4 16% 22% 13% 2	5307
	21st to end	Night	55% 5% 9% 18% 12% 1	4962
April	1st to 10th	Night	50% 6% 7% 18% 18% 1	2000
	11th to 20th	Night	46% 5% 9% 21% 15% 3	1975
	21st to end	Night	46% 6% 11% 21% 15% 2	1863
May	1st to 10th	Night	41% 6% 13% 18% 18% 3	3844
	11th to 20th	Night	33% 9% 14% 24% 18% 2	3597
	21st to end	Night	45% 7% 10% 22% 13% 3	3950
June	1st to 10th	Night	34% 6% 13% 30% 17% 1	1600
	11th to 20th	Night	40% 6% 11% 24% 17% 1	1600
	21st to end	Night	33% 8% 15% 26% 14% 4	1600
July	1st to 10th	Night	35% 7% 14% 31% 9% 3	3580
	11th to 20th	Night	26% 7% 15% 34% 15% 2	3572
	21st to end	Night	30% 7% 15% 24% 22% 2	3832
August	1st to 10th	Night	34% 7% 13% 27% 18% 1	2588
	11th to 20th	Night	36% 8% 12% 29% 15% 1	3033
	21st to end	Night	33% 7% 14% 24% 20% 3	3586
September	1st to 10th	Night	31% 6% 12% 28% 22% 1	2000
	11th to 20th	Night	31% 7% 12% 34% 15% 1	2070
	21st to end	Night	35% 7% 11% 31% 15% 1	2200
October	1st to 10th	Night	27% 4 7% 37% 22% 2	3788
	11th to 20th	Night	35% 5% 11% 30% 16% 2	3948
	21st to end	Night	46% 4 10% 24% 16%	4610
November	1st to 10th	Night	41% 5% 12% 25% 15% 2	2666
	11th to 20th	Night	51% 4 13% 19% 12% 2	2756
	21st to end	Night	48% 6% 14% 23% 8% 1	2940
December	1st to 10th	Night	44% 6% 19% 23% 6% 2	4609
	11th to 20th	Night	60% 4 9% 14% 12% 1	5201
	21st to end	Night	65% 5% 8% 14% 7%	6996

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	14% 10% 37% 27% 10% 2	300
	11th to 20th	Day	20% 11% 35% 26% 7% 1	300
	21st to end	Day	18% 12% 35% 28% 7% 1	330
February	1st to 10th	Day	15% 12% 39% 25% 7% 2	300
	11th to 20th	Day	16% 17% 41% 18% 8%	300
	21st to end	Day	15% 18% 47% 18% 2	249
March	1st to 10th	Day	19% 15% 38% 22% 7%	300
	11th to 20th	Day	21% 16% 32% 21% 8% 2	300
	21st to end	Day	26% 11% 28% 26% 8% 1	549
April	1st to 10th	Day	25% 14% 32% 22% 6%	500
	11th to 20th	Day	24% 17% 28% 18% 10% 3	492
	21st to end	Day	24% 12% 27% 23% 12% 2	500
May	1st to 10th	Day	18% 11% 32% 28% 10% 2	596
	11th to 20th	Day	18% 11% 28% 27% 11% 4	725
	21st to end	Day	17% 9% 27% 27% 13% 6%	789
June	1st to 10th	Day	12% 9% 29% 30% 16% 4	730
	11th to 20th	Day	15% 9% 30% 29% 12% 5%	730
	21st to end	Day	12% 9% 28% 30% 16% 4	730
July	1st to 10th	Day	8% 4 20% 34% 26% 9%	721
	11th to 20th	Day	9% 6% 24% 33% 19% 8%	718
	21st to end	Day	8% 4 24% 33% 22% 8%	794
August	1st to 10th	Day	10% 3 24% 29% 24% 11%	726
	11th to 20th	Day	13% 6% 16% 24% 28% 12%	576
	21st to end	Day	13% 7% 22% 25% 23% 10%	583
September	1st to 10th	Day	13% 7% 24% 26% 20% 10%	530
	11th to 20th	Day	12% 3 21% 32% 24% 8%	530
	21st to end	Day	14% 9% 26% 23% 22% 5%	530
October	1st to 10th	Day	15% 11% 25% 26% 17% 5%	405
	11th to 20th	Day	21% 16% 32% 22% 9% 1	330
	21st to end	Day	19% 15% 36% 23% 5% 1	363
November	1st to 10th	Day	15% 15% 35% 25% 9% 2	330
	11th to 20th	Day	17% 19% 36% 16% 10% 1	330
	21st to end	Day	22% 13% 43% 18% 5%	330
December	1st to 10th	Day	15% 16% 42% 20% 7% 1	306
	11th to 20th	Day	21% 16% 37% 19% 5% 1	300
	21st to end	Day	26% 18% 32% 18% 5% 1	330
January	1st to 10th	Night	16% 11% 35% 29% 8% 1	1000
	11th to 20th	Night	20% 11% 36% 25% 6% 1	1000
	21st to end	Night	20% 8% 35% 30% 7%	1100
February	1st to 10th	Night	16% 11% 36% 30% 7% 1	1000
	11th to 20th	Night	16% 11% 41% 24% 8%	846
	21st to end	Night	20% 11% 36% 28% 4	660
March	1st to 10th	Night	19% 9% 33% 30% 8% 1	800
	11th to 20th	Night	16% 12% 37% 26% 8% 1	745
	21st to end	Night	22% 8% 31% 31% 7% 1	660
April	1st to 10th	Night	23% 10% 36% 25% 6%	600
	11th to 20th	Night	24% 10% 29% 30% 6% 1	593
	21st to end	Night	21% 7% 33% 32% 7% 1	600
May	1st to 10th	Night	22% 7% 33% 30% 8%	600
	11th to 20th	Night	17% 8% 32% 34% 8% 1	591
	21st to end	Night	15% 5% 26% 37% 17%	650
June	1st to 10th	Night	10% 6% 29% 40% 15%	600
	11th to 20th	Night	13% 5% 30% 40% 11% 1	600
	21st to end	Night	11% 5% 26% 44% 15% 1	600
July	1st to 10th	Night	8% 4 18% 45% 23% 2	585
	11th to 20th	Night	8% 5% 20% 43% 22% 2	582
	21st to end	Night	6% 3 20% 46% 24% 2	657
August	1st to 10th	Night	9% 3 16% 45% 25% 2	597
	11th to 20th	Night	11% 3 17% 38% 29% 3	594
	21st to end	Night	10% 3 22% 40% 23% 2	660
September	1st to 10th	Night	11% 4 23% 39% 19% 5%	600
	11th to 20th	Night	13% 4 24% 31% 26% 3	670
	21st to end	Night	13% 8% 24% 34% 20% 2	800
October	1st to 10th	Night	15% 8% 27% 30% 19% 1	800
	11th to 20th	Night	20% 11% 33% 27% 9%	800
	21st to end	Night	23% 10% 30% 27% 9% 1	880
November	1st to 10th	Night	19% 10% 35% 27% 9% 1	820
	11th to 20th	Night	19% 15% 36% 23% 6%	866
	21st to end	Night	21% 12% 35% 25% 7%	1050
December	1st to 10th	Night	19% 11% 39% 25% 6%	1011
	11th to 20th	Night	22% 11% 34% 26% 6% 1	1000
	21st to end	Night	27% 11% 31% 26% 5%	1100

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