Hemlock Crossings Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hemlock Crossings Park clear sky chart from 2005-11-06 to 2026-10-14.

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	13% 10% 4 9% 5% 4 4 3 5% 7% 36%	149223
	Night	14% 13% 5% 11% 6% 5% 4 3 4 6% 31%	142814
Transparency	Day	47% 6% 12% 22% 13% 1	152749
	Night	54% 5% 10% 18% 11% 1	147365
Seeing	Day	17% 10% 26% 28% 15% 5%	18541
	Night	20% 9% 26% 29% 14% 2	28303

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	14% 23% 12% 24% 6% 4 3 2 2 2 8%	4691
	11th to 20th	Day	9% 15% 8% 26% 16% 10% 3 2 3 2 6%	4710
	21st to end	Day	12% 17% 7% 20% 11% 6% 7% 2 2 2 13%	5156
February	1st to 10th	Day	11% 16% 6% 17% 11% 6% 5% 3 4 4 18%	1923
	11th to 20th	Day	13% 14% 6% 15% 10% 5% 4 3 4 5% 21%	2048
	21st to end	Day	15% 15% 6% 12% 7% 6% 4 4 5% 6% 22%	1730
March	1st to 10th	Day	13% 10% 4 12% 5% 5% 4 3 5% 6% 33%	4580
	11th to 20th	Day	11% 8% 5% 9% 5% 4 4 4 5% 8% 37%	4896
	21st to end	Day	19% 14% 7% 9% 5% 3 4 3 4 5% 27%	5878
April	1st to 10th	Day	19% 12% 4 7% 5% 4 4 4 5% 6% 32%	2520
	11th to 20th	Day	16% 10% 3 7% 4 4 4 4 5% 7% 37%	2530
	21st to end	Day	16% 9% 3 7% 4 4 4 4 5% 7% 36%	2730
May	1st to 10th	Day	15% 7% 2 6% 4 4 4 3 5% 8% 42%	7616
	11th to 20th	Day	13% 7% 3 7% 4 4 4 3 6% 9% 41%	7742
	21st to end	Day	13% 6% 2 5% 4 3 3 3 5% 8% 48%	9047
June	1st to 10th	Day	10% 5% 2 5% 4 5% 4 3 6% 8% 47%	2940
	11th to 20th	Day	10% 5% 2 6% 4 4 4 3 5% 9% 49%	2940
	21st to end	Day	10% 6% 2 6% 3 4 4 4 6% 8% 47%	2940
July	1st to 10th	Day	10% 6% 3 6% 4 4 5% 4 5% 9% 44%	8280
	11th to 20th	Day	6% 4 2 4 3 3 4 4 6% 10% 54%	8280
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 9% 50%	8990
August	1st to 10th	Day	14% 6% 2 6% 3 4 4 4 6% 9% 42%	6154
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 6% 7% 44%	5936
	21st to end	Day	7% 5% 2 7% 4 4 4 4 6% 8% 48%	6080
September	1st to 10th	Day	10% 6% 2 5% 5% 4 4 3 6% 8% 46%	2510
	11th to 20th	Day	11% 5% 2 5% 3 4 4 4 6% 8% 49%	2310
	21st to end	Day	12% 6% 3 7% 5% 5% 5% 3 5% 8% 43%	2310
October	1st to 10th	Day	15% 7% 2 6% 5% 4 4 2 4 6% 45%	2310
	11th to 20th	Day	21% 11% 3 7% 5% 5% 5% 4 5% 6% 26%	1970
	21st to end	Day	22% 12% 3 9% 6% 5% 4 3 5% 6% 25%	1980
November	1st to 10th	Day	14% 13% 3 8% 5% 4 4 3 6% 6% 34%	1852
	11th to 20th	Day	17% 20% 6% 12% 5% 5% 4 3 5% 4 21%	1890
	21st to end	Day	21% 20% 6% 10% 5% 3 4 3 3 5% 20%	1890
December	1st to 10th	Day	11% 27% 13% 14% 5% 4 3 2 3 5% 13%	2706
	11th to 20th	Day	16% 25% 12% 14% 8% 4 3 3 3 3 9%	3088
	21st to end	Day	23% 24% 7% 13% 6% 4 3 3 4 4 11%	4070
January	1st to 10th	Night	12% 22% 12% 24% 6% 4 2 2 3 3 11%	8232
	11th to 20th	Night	10% 20% 12% 25% 11% 8% 3 2 2 2 6%	8280
	21st to end	Night	13% 17% 9% 19% 10% 8% 6% 2 3 3 10%	9058
February	1st to 10th	Night	12% 19% 6% 16% 9% 5% 3 3 3 4 19%	2690
	11th to 20th	Night	14% 16% 7% 14% 8% 5% 4 3 3 4 22%	2458
	21st to end	Night	17% 16% 4 12% 6% 5% 4 4 4 5% 24%	2076
March	1st to 10th	Night	15% 9% 3 9% 5% 5% 4 3 6% 6% 35%	5493
	11th to 20th	Night	11% 8% 3 8% 5% 4 4 3 5% 8% 42%	5283
	21st to end	Night	18% 11% 5% 10% 5% 4 3 3 4 5% 30%	5336
April	1st to 10th	Night	16% 10% 3 7% 5% 4 5% 4 6% 6% 34%	2100
	11th to 20th	Night	20% 10% 2 6% 4 4 4 4 5% 6% 35%	2039
	21st to end	Night	16% 7% 3 6% 4 4 5% 4 6% 7% 38%	1890
May	1st to 10th	Night	13% 8% 3 8% 6% 4 5% 4 5% 6% 38%	5237
	11th to 20th	Night	12% 6% 2 6% 4 3 4 4 6% 8% 43%	5121
	21st to end	Night	15% 6% 2 6% 4 4 4 3 5% 6% 43%	5139
June	1st to 10th	Night	10% 6% 2 5% 5% 5% 5% 5% 6% 8% 44%	1680
	11th to 20th	Night	9% 7% 2 7% 5% 5% 5% 4 6% 9% 43%	1680
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 7% 9% 44%	1680
July	1st to 10th	Night	9% 6% 2 7% 5% 5% 5% 4 6% 8% 43%	4708
	11th to 20th	Night	5% 5% 1 5% 4 4 3 4 6% 9% 56%	4707
	21st to end	Night	9% 6% 2 6% 4 4 4 3 5% 7% 49%	5117
August	1st to 10th	Night	13% 6% 3 6% 4 3 4 3 5% 7% 45%	4000
	11th to 20th	Night	12% 6% 3 7% 5% 4 4 4 5% 8% 43%	4095
	21st to end	Night	7% 5% 2 7% 4 5% 5% 4 5% 8% 46%	5044
September	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 6% 7% 50%	2100
	11th to 20th	Night	11% 4 2 5% 4 3 3 3 5% 6% 54%	2299
	21st to end	Night	12% 8% 2 7% 5% 5% 4 3 5% 7% 43%	2310
October	1st to 10th	Night	18% 6% 2 5% 4 3 4 3 4 6% 47%	2310
	11th to 20th	Night	22% 11% 3 7% 4 4 3 3 4 6% 34%	2491
	21st to end	Night	25% 11% 3 6% 3 3 3 3 4 5% 32%	2860
November	1st to 10th	Night	16% 13% 3 7% 5% 4 4 3 4 6% 34%	2666
	11th to 20th	Night	19% 18% 6% 10% 4 4 3 3 5% 5% 22%	2730
	21st to end	Night	18% 22% 7% 11% 4 3 4 3 3 5% 21%	2730
December	1st to 10th	Night	13% 27% 9% 16% 6% 4 3 2 4 4 13%	4686
	11th to 20th	Night	17% 26% 9% 16% 6% 3 3 2 3 3 10%	5339
	21st to end	Night	24% 23% 6% 11% 4 4 4 3 4 5% 12%	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	84% 5% 4 6% 1	4692
	11th to 20th	Day	86% 5% 5% 3 1	4710
	21st to end	Day	78% 5% 7% 8% 3	5156
February	1st to 10th	Day	70% 6% 7% 13% 3	1923
	11th to 20th	Day	66% 5% 11% 13% 5% 1	2058
	21st to end	Day	62% 7% 13% 13% 5%	1730
March	1st to 10th	Day	51% 5% 15% 19% 9% 1	4580
	11th to 20th	Day	45% 5% 18% 22% 10% 1	4896
	21st to end	Day	59% 4 11% 16% 10% 1	5880
April	1st to 10th	Day	53% 6% 11% 19% 11%	2520
	11th to 20th	Day	46% 6% 10% 22% 14% 2	2530
	21st to end	Day	45% 6% 13% 21% 14% 2	2730
May	1st to 10th	Day	40% 6% 11% 26% 16% 1	7651
	11th to 20th	Day	40% 7% 13% 22% 16% 2	7746
	21st to end	Day	35% 5% 10% 25% 21% 3	9061
June	1st to 10th	Day	34% 6% 12% 28% 18% 2	2940
	11th to 20th	Day	32% 7% 15% 24% 20% 1	2940
	21st to end	Day	34% 7% 16% 25% 17% 2	2940
July	1st to 10th	Day	36% 6% 14% 27% 15% 2	8211
	11th to 20th	Day	27% 4 13% 32% 22% 1	8205
	21st to end	Day	30% 5% 15% 27% 22% 1	8794
August	1st to 10th	Day	39% 5% 12% 28% 14% 1	6139
	11th to 20th	Day	37% 6% 15% 29% 12% 1	5975
	21st to end	Day	33% 5% 15% 32% 14% 1	6079
September	1st to 10th	Day	35% 7% 15% 28% 14% 2	2510
	11th to 20th	Day	33% 6% 13% 29% 16% 2	2310
	21st to end	Day	40% 5% 12% 26% 16% 1	2310
October	1st to 10th	Day	29% 4 8% 40% 18% 1	3700
	11th to 20th	Day	43% 6% 13% 24% 14%	3160
	21st to end	Day	51% 5% 13% 21% 9% 1	3180
November	1st to 10th	Day	51% 7% 12% 20% 11%	1852
	11th to 20th	Day	66% 6% 9% 13% 5% 1	1890
	21st to end	Day	68% 5% 12% 11% 4	1890
December	1st to 10th	Day	76% 7% 9% 7% 2	2706
	11th to 20th	Day	81% 5% 8% 5% 1	3085
	21st to end	Day	77% 6% 6% 9% 2	4070
January	1st to 10th	Night	79% 5% 6% 7% 3	8233
	11th to 20th	Night	88% 4 4 2 2	8280
	21st to end	Night	80% 5% 7% 5% 2	9058
February	1st to 10th	Night	70% 5% 9% 11% 5%	2690
	11th to 20th	Night	67% 5% 7% 16% 5%	2459
	21st to end	Night	62% 5% 11% 14% 6% 1	2076
March	1st to 10th	Night	48% 6% 13% 23% 8% 1	5493
	11th to 20th	Night	40% 6% 14% 27% 11% 2	5283
	21st to end	Night	55% 5% 9% 18% 12% 1	5336
April	1st to 10th	Night	49% 7% 11% 18% 14% 1	2100
	11th to 20th	Night	49% 5% 8% 17% 18% 3	2039
	21st to end	Night	43% 7% 11% 21% 14% 3	1890
May	1st to 10th	Night	45% 5% 11% 21% 15% 3	5264
	11th to 20th	Night	38% 7% 12% 23% 18% 3	5122
	21st to end	Night	41% 6% 7% 20% 21% 5%	5149
June	1st to 10th	Night	35% 7% 10% 27% 18% 3	1680
	11th to 20th	Night	37% 6% 12% 24% 19% 2	1680
	21st to end	Night	35% 8% 14% 25% 16% 3	1680
July	1st to 10th	Night	38% 6% 12% 27% 14% 4	4670
	11th to 20th	Night	26% 5% 12% 29% 27% 2	4662
	21st to end	Night	34% 5% 11% 24% 24% 2	5002
August	1st to 10th	Night	38% 5% 11% 26% 19% 1	3991
	11th to 20th	Night	39% 7% 12% 28% 13% 1	4122
	21st to end	Night	35% 6% 11% 30% 17% 1	5044
September	1st to 10th	Night	34% 6% 13% 27% 18% 2	2100
	11th to 20th	Night	31% 5% 11% 32% 20% 2	2299
	21st to end	Night	41% 7% 11% 26% 13% 2	2310
October	1st to 10th	Night	31% 4 8% 35% 21% 1	3700
	11th to 20th	Night	42% 5% 12% 24% 17%	4040
	21st to end	Night	46% 5% 9% 26% 15%	4610
November	1st to 10th	Night	52% 7% 9% 20% 11% 1	2666
	11th to 20th	Night	64% 6% 10% 14% 6% 1	2730
	21st to end	Night	67% 6% 12% 14% 2	2730
December	1st to 10th	Night	75% 7% 9% 6% 2	4686
	11th to 20th	Night	80% 5% 8% 5% 2	5341
	21st to end	Night	74% 5% 9% 9% 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	22% 13% 35% 23% 5% 2	330
	11th to 20th	Day	22% 20% 32% 20% 6% 1	330
	21st to end	Day	29% 13% 29% 24% 5% 1	363
February	1st to 10th	Day	18% 18% 38% 18% 7% 2	330
	11th to 20th	Day	20% 18% 35% 20% 6% 1	330
	21st to end	Day	24% 14% 40% 17% 5%	273
March	1st to 10th	Day	20% 15% 38% 20% 6%	330
	11th to 20th	Day	21% 15% 28% 25% 10% 1	450
	21st to end	Day	26% 13% 27% 25% 7% 1	594
April	1st to 10th	Day	25% 11% 30% 26% 7%	540
	11th to 20th	Day	21% 17% 29% 23% 8% 3	532
	21st to end	Day	22% 8% 30% 26% 12% 2	540
May	1st to 10th	Day	19% 11% 29% 27% 11% 2	543
	11th to 20th	Day	17% 9% 23% 29% 18% 4	605
	21st to end	Day	14% 5% 25% 29% 21% 6%	844
June	1st to 10th	Day	11% 4 27% 35% 19% 4	780
	11th to 20th	Day	13% 8% 22% 34% 19% 4	780
	21st to end	Day	11% 6% 25% 36% 17% 4	780
July	1st to 10th	Day	7% 3 22% 33% 25% 10%	771
	11th to 20th	Day	9% 4 22% 35% 23% 7%	768
	21st to end	Day	9% 3 20% 40% 22% 6%	849
August	1st to 10th	Day	11% 3 15% 31% 29% 11%	629
	11th to 20th	Day	11% 6% 15% 31% 26% 11%	559
	21st to end	Day	11% 5% 16% 31% 27% 10%	627
September	1st to 10th	Day	14% 6% 16% 32% 23% 9%	570
	11th to 20th	Day	10% 5% 15% 26% 28% 16%	570
	21st to end	Day	16% 7% 23% 23% 22% 10%	570
October	1st to 10th	Day	16% 8% 27% 25% 17% 6%	570
	11th to 20th	Day	24% 14% 26% 27% 8% 1	408
	21st to end	Day	29% 12% 31% 21% 5% 1	363
November	1st to 10th	Day	23% 16% 27% 24% 8% 2	330
	11th to 20th	Day	27% 20% 30% 19% 4	330
	21st to end	Day	28% 17% 36% 15% 4	330
December	1st to 10th	Day	25% 22% 27% 19% 6% 1	330
	11th to 20th	Day	23% 24% 29% 19% 4 1	330
	21st to end	Day	30% 19% 32% 15% 3 2	363
January	1st to 10th	Night	23% 16% 32% 22% 7%	1050
	11th to 20th	Night	25% 15% 31% 22% 6%	1050
	21st to end	Night	23% 12% 33% 26% 6%	1155
February	1st to 10th	Night	21% 11% 35% 27% 5% 1	905
	11th to 20th	Night	23% 11% 33% 26% 7%	823
	21st to end	Night	24% 13% 36% 23% 3	692
March	1st to 10th	Night	20% 10% 31% 30% 8%	840
	11th to 20th	Night	18% 10% 31% 31% 9% 1	840
	21st to end	Night	21% 10% 29% 29% 11%	814
April	1st to 10th	Night	20% 9% 32% 31% 8% 1	630
	11th to 20th	Night	25% 10% 24% 30% 10% 1	623
	21st to end	Night	19% 6% 29% 34% 10% 2	630
May	1st to 10th	Night	17% 6% 26% 37% 13% 1	630
	11th to 20th	Night	19% 4 24% 32% 20% 1	621
	21st to end	Night	16% 3 19% 35% 23% 4	683
June	1st to 10th	Night	12% 3 22% 40% 21% 2	630
	11th to 20th	Night	12% 4 23% 37% 22% 2	630
	21st to end	Night	11% 3 19% 39% 26% 2	630
July	1st to 10th	Night	8% 2 14% 35% 35% 6%	615
	11th to 20th	Night	7% 2 15% 40% 31% 5%	612
	21st to end	Night	9% 2 15% 40% 32% 3	690
August	1st to 10th	Night	8% 2 12% 42% 30% 5%	627
	11th to 20th	Night	11% 3 11% 39% 29% 6%	624
	21st to end	Night	11% 2 14% 37% 32% 4	693
September	1st to 10th	Night	12% 4 15% 37% 28% 4	630
	11th to 20th	Night	12% 4 14% 33% 31% 7%	829
	21st to end	Night	15% 6% 23% 27% 24% 5%	840
October	1st to 10th	Night	21% 5% 22% 32% 19% 3	840
	11th to 20th	Night	28% 11% 24% 26% 11% 1	813
	21st to end	Night	30% 10% 30% 22% 6% 1	880
November	1st to 10th	Night	24% 11% 29% 25% 10% 1	820
	11th to 20th	Night	28% 17% 30% 20% 5%	840
	21st to end	Night	29% 15% 30% 23% 4	840
December	1st to 10th	Night	28% 16% 32% 19% 5%	1029
	11th to 20th	Night	28% 15% 33% 19% 4	1050
	21st to end	Night	33% 12% 35% 18% 2	1155

Page generated at 2026-10-11 05:06:31. Version ac07

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