Jerimoth Hill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jerimoth Hill clear sky chart from 2005-11-06 to 2025-07-21.

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% 8% 2 6% 4 4 4 3 5% 7% 38%	119727
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 39%	119382
Transparency	Day	45% 5% 11% 21% 15% 3	123318
	Night	44% 5% 11% 21% 16% 3	123952
Seeing	Day	24% 18% 32% 18% 7% 2	15955
	Night	22% 16% 34% 21% 6%	24884

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% 9% 2 8% 4 4 4 3 5% 5% 44%	3597
	11th to 20th	Day	15% 8% 2 6% 4 3 5% 3 4 5% 46%	3570
	21st to end	Day	18% 9% 2 6% 3 4 4 3 4 4 43%	3960
February	1st to 10th	Day	18% 8% 3 5% 5% 5% 5% 4 5% 7% 36%	1901
	11th to 20th	Day	14% 8% 2 6% 5% 5% 5% 4 4 7% 40%	1948
	21st to end	Day	19% 10% 2 6% 4 4 4 2 4 6% 38%	1650
March	1st to 10th	Day	21% 11% 3 6% 3 3 3 2 4 6% 37%	4476
	11th to 20th	Day	14% 8% 2 6% 4 4 5% 4 5% 8% 40%	4736
	21st to end	Day	22% 11% 2 5% 4 4 4 4 5% 6% 33%	5832
April	1st to 10th	Day	19% 11% 2 6% 4 3 4 3 4 7% 36%	2400
	11th to 20th	Day	17% 7% 2 5% 4 4 4 4 5% 7% 40%	2374
	21st to end	Day	20% 7% 2 6% 4 4 4 3 5% 5% 37%	2580
May	1st to 10th	Day	29% 11% 3 7% 4 4 4 3 5% 7% 25%	5886
	11th to 20th	Day	21% 10% 3 8% 4 4 4 3 5% 6% 32%	5984
	21st to end	Day	20% 7% 3 6% 5% 4 4 4 6% 7% 34%	6949
June	1st to 10th	Day	19% 7% 2 6% 5% 4 5% 4 6% 8% 35%	2800
	11th to 20th	Day	16% 8% 2 6% 5% 4 5% 4 6% 8% 36%	2800
	21st to end	Day	16% 7% 2 7% 4 4 6% 5% 6% 8% 36%	2800
July	1st to 10th	Day	14% 7% 2 7% 6% 6% 6% 5% 6% 9% 33%	4580
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 5% 7% 9% 37%	4580
	21st to end	Day	20% 8% 2 7% 5% 4 5% 4 6% 7% 32%	4814
August	1st to 10th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 8% 30%	4169
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 5% 7% 39%	3900
	21st to end	Day	7% 4 2 7% 5% 5% 6% 5% 7% 9% 43%	4180
September	1st to 10th	Day	15% 6% 2 6% 4 5% 5% 3 6% 5% 45%	2280
	11th to 20th	Day	15% 5% 2 5% 4 4 3 3 4 5% 51%	2101
	21st to end	Day	18% 7% 2 6% 4 4 3 3 5% 6% 42%	2090
October	1st to 10th	Day	21% 8% 2 5% 4 3 3 3 5% 6% 41%	2090
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 4 7% 48%	1865
	21st to end	Day	18% 6% 3 6% 4 3 3 3 5% 6% 42%	1881
November	1st to 10th	Day	15% 6% 2 5% 4 3 3 3 4 4 49%	1761
	11th to 20th	Day	18% 7% 1 3 4 3 3 3 5% 5% 48%	1800
	21st to end	Day	18% 8% 2 6% 3 3 4 3 5% 6% 44%	1800
December	1st to 10th	Day	14% 9% 2 5% 3 3 4 3 5% 6% 46%	2647
	11th to 20th	Day	20% 6% 2 5% 3 3 3 3 4 5% 48%	2986
	21st to end	Day	20% 11% 3 7% 3 4 3 3 4 5% 39%	3960
January	1st to 10th	Night	14% 6% 2 6% 3 4 4 3 5% 7% 46%	6349
	11th to 20th	Night	15% 9% 3 8% 4 4 4 3 4 4 42%	6315
	21st to end	Night	16% 9% 3 6% 5% 4 5% 3 5% 5% 38%	6996
February	1st to 10th	Night	17% 9% 3 7% 5% 4 4 3 5% 6% 39%	2495
	11th to 20th	Night	16% 8% 2 7% 5% 4 3 3 5% 6% 40%	2338
	21st to end	Night	18% 10% 3 7% 4 3 3 4 4 6% 39%	1980
March	1st to 10th	Night	22% 9% 2 5% 3 3 4 3 5% 6% 38%	5364
	11th to 20th	Night	16% 9% 3 7% 4 4 4 3 4 7% 40%	5221
	21st to end	Night	22% 11% 2 5% 3 4 4 4 5% 5% 34%	5083
April	1st to 10th	Night	19% 9% 2 6% 5% 4 5% 4 5% 6% 36%	2000
	11th to 20th	Night	20% 8% 3 6% 4 4 3 3 5% 6% 38%	1975
	21st to end	Night	21% 7% 3 6% 3 3 3 3 4 6% 40%	1820
May	1st to 10th	Night	28% 10% 3 7% 4 4 4 3 5% 7% 25%	4054
	11th to 20th	Night	19% 10% 3 9% 6% 5% 5% 4 5% 7% 28%	3951
	21st to end	Night	21% 8% 3 7% 4 5% 4 4 6% 7% 32%	3926
June	1st to 10th	Night	17% 8% 3 6% 4 4 4 4 5% 7% 38%	1600
	11th to 20th	Night	19% 8% 3 5% 5% 4 4 3 6% 8% 37%	1600
	21st to end	Night	14% 8% 2 5% 3 4 5% 4 6% 8% 41%	1600
July	1st to 10th	Night	15% 8% 2 6% 5% 5% 6% 5% 7% 8% 34%	2600
	11th to 20th	Night	17% 8% 3 6% 4 3 4 4 6% 9% 37%	2600
	21st to end	Night	19% 10% 3 7% 5% 4 4 3 5% 6% 33%	2739
August	1st to 10th	Night	24% 8% 2 7% 4 5% 5% 4 6% 6% 28%	2730
	11th to 20th	Night	11% 8% 3 8% 5% 6% 6% 5% 6% 8% 34%	2910
	21st to end	Night	9% 5% 2 4 3 3 3 3 5% 8% 56%	3476
September	1st to 10th	Night	14% 6% 3 7% 4 4 5% 3 5% 6% 43%	1900
	11th to 20th	Night	13% 7% 2 5% 3 3 3 2 3 7% 51%	2077
	21st to end	Night	17% 8% 2 7% 4 4 4 3 5% 5% 41%	2090
October	1st to 10th	Night	19% 8% 3 5% 4 2 3 3 5% 6% 41%	2090
	11th to 20th	Night	16% 5% 2 5% 3 3 4 3 5% 6% 47%	2313
	21st to end	Night	20% 8% 3 6% 4 4 4 2 5% 5% 40%	2717
November	1st to 10th	Night	13% 6% 2 6% 4 3 4 3 5% 6% 48%	2537
	11th to 20th	Night	17% 8% 2 5% 3 3 3 3 4 5% 46%	2600
	21st to end	Night	17% 7% 2 5% 3 3 3 3 5% 7% 45%	2600
December	1st to 10th	Night	17% 9% 2 5% 4 3 3 2 3 4 47%	4532
	11th to 20th	Night	24% 7% 2 6% 3 3 3 3 4 4 41%	5208
	21st to end	Night	18% 10% 3 7% 4 3 3 3 4 5% 41%	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	39% 4 7% 28% 19% 3	3598
	11th to 20th	Day	40% 5% 9% 21% 17% 8%	3600
	21st to end	Day	45% 3 9% 21% 19% 2	3960
February	1st to 10th	Day	47% 5% 12% 19% 14% 3	1901
	11th to 20th	Day	44% 6% 9% 22% 16% 3	1957
	21st to end	Day	49% 4 9% 20% 16% 3	1650
March	1st to 10th	Day	48% 4 10% 15% 12% 10%	4479
	11th to 20th	Day	40% 7% 13% 28% 11% 2	4736
	21st to end	Day	52% 4 6% 15% 16% 6%	5832
April	1st to 10th	Day	47% 5% 10% 19% 16% 3	2400
	11th to 20th	Day	42% 6% 10% 20% 19% 3	2374
	21st to end	Day	47% 5% 8% 19% 16% 4	2580
May	1st to 10th	Day	59% 6% 13% 12% 9% 1	5897
	11th to 20th	Day	52% 5% 13% 17% 11% 1	5988
	21st to end	Day	47% 6% 12% 21% 13% 1	6949
June	1st to 10th	Day	46% 7% 12% 23% 12% 1	2800
	11th to 20th	Day	44% 6% 14% 21% 13% 2	2800
	21st to end	Day	43% 8% 12% 21% 14% 1	2800
July	1st to 10th	Day	46% 7% 11% 20% 14% 1	4510
	11th to 20th	Day	43% 6% 16% 23% 11% 2	4505
	21st to end	Day	51% 5% 11% 18% 12% 2	4661
August	1st to 10th	Day	51% 6% 16% 19% 8%	4155
	11th to 20th	Day	42% 6% 13% 28% 10% 1	3939
	21st to end	Day	35% 7% 12% 28% 16% 2	4180
September	1st to 10th	Day	39% 6% 11% 22% 19% 2	2280
	11th to 20th	Day	35% 5% 8% 24% 24% 3	2101
	21st to end	Day	44% 5% 9% 20% 22% 2	2090
October	1st to 10th	Day	40% 4 8% 21% 22% 4	3480
	11th to 20th	Day	30% 4 8% 24% 31% 5%	3081
	21st to end	Day	32% 4 13% 28% 20% 3	3081
November	1st to 10th	Day	40% 4 12% 22% 20% 2	1761
	11th to 20th	Day	38% 5% 11% 21% 22% 4	1800
	21st to end	Day	42% 5% 11% 27% 12% 3	1800
December	1st to 10th	Day	39% 4 14% 28% 13% 1	2647
	11th to 20th	Day	40% 3 14% 18% 20% 5%	2986
	21st to end	Day	49% 4 7% 20% 14% 5%	3960
January	1st to 10th	Night	36% 4 10% 31% 17% 2	6349
	11th to 20th	Night	45% 4 11% 20% 14% 5%	6360
	21st to end	Night	48% 4 10% 17% 17% 4	6996
February	1st to 10th	Night	46% 4 13% 22% 13% 2	2495
	11th to 20th	Night	45% 5% 9% 19% 18% 4	2340
	21st to end	Night	46% 5% 8% 22% 15% 4	1980
March	1st to 10th	Night	47% 4 9% 18% 16% 7%	5374
	11th to 20th	Night	44% 5% 17% 19% 12% 3	5222
	21st to end	Night	51% 4 6% 13% 21% 6%	5083
April	1st to 10th	Night	48% 6% 10% 18% 15% 4	2000
	11th to 20th	Night	46% 5% 9% 19% 18% 2	1975
	21st to end	Night	45% 6% 9% 20% 15% 5%	1820
May	1st to 10th	Night	57% 8% 15% 11% 9% 1	4060
	11th to 20th	Night	53% 8% 13% 15% 9% 2	3952
	21st to end	Night	50% 7% 13% 19% 10% 1	3927
June	1st to 10th	Night	44% 8% 13% 20% 14% 1	1600
	11th to 20th	Night	45% 7% 13% 23% 12% 1	1600
	21st to end	Night	39% 7% 16% 23% 13% 1	1600
July	1st to 10th	Night	45% 8% 13% 21% 13% 1	2560
	11th to 20th	Night	43% 6% 17% 25% 9% 1	2552
	21st to end	Night	52% 5% 12% 16% 14% 1	2651
August	1st to 10th	Night	54% 8% 12% 17% 8% 1	2720
	11th to 20th	Night	45% 8% 14% 25% 8%	2937
	21st to end	Night	27% 5% 15% 30% 20% 2	3476
September	1st to 10th	Night	41% 7% 10% 23% 18% 2	1900
	11th to 20th	Night	35% 5% 10% 22% 26% 2	2077
	21st to end	Night	46% 5% 9% 19% 19% 3	2090
October	1st to 10th	Night	40% 4 13% 23% 17% 2	3480
	11th to 20th	Night	27% 4 9% 26% 32% 3	3836
	21st to end	Night	34% 3 11% 29% 19% 3	4467
November	1st to 10th	Night	36% 6% 12% 22% 20% 4	2537
	11th to 20th	Night	41% 4 9% 22% 21% 4	2600
	21st to end	Night	39% 5% 14% 27% 14% 2	2600
December	1st to 10th	Night	42% 3 11% 29% 14% 1	4532
	11th to 20th	Night	47% 4 13% 14% 20% 2	5208
	21st to end	Night	46% 4 7% 21% 17% 4	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	32% 25% 29% 12% 3	200
	11th to 20th	Day	32% 25% 31% 9% 4	200
	21st to end	Day	26% 29% 32% 9% 3	220
February	1st to 10th	Day	34% 25% 30% 11% 1	417
	11th to 20th	Day	31% 31% 31% 6% 1	496
	21st to end	Day	31% 26% 30% 10% 3	414
March	1st to 10th	Day	31% 25% 31% 11% 2	500
	11th to 20th	Day	29% 26% 31% 11% 3	500
	21st to end	Day	31% 24% 30% 10% 3 1	550
April	1st to 10th	Day	35% 23% 26% 10% 5% 1	500
	11th to 20th	Day	31% 22% 34% 11% 3	492
	21st to end	Day	29% 22% 30% 14% 3 2	500
May	1st to 10th	Day	35% 20% 28% 14% 2 1	503
	11th to 20th	Day	23% 17% 41% 14% 5%	527
	21st to end	Day	20% 14% 34% 23% 6% 2	573
June	1st to 10th	Day	21% 14% 35% 22% 6% 2	530
	11th to 20th	Day	17% 16% 37% 21% 7% 1	530
	21st to end	Day	18% 13% 36% 24% 7% 2	530
July	1st to 10th	Day	17% 10% 31% 26% 14% 2	525
	11th to 20th	Day	16% 9% 31% 30% 13% 2	524
	21st to end	Day	15% 10% 39% 26% 9% 1	532
August	1st to 10th	Day	13% 10% 35% 29% 10% 2	486
	11th to 20th	Day	15% 9% 32% 28% 12% 4	479
	21st to end	Day	11% 12% 32% 26% 14% 5%	539
September	1st to 10th	Day	20% 11% 27% 23% 15% 4	490
	11th to 20th	Day	17% 10% 29% 23% 13% 8%	490
	21st to end	Day	26% 10% 35% 18% 8% 3	490
October	1st to 10th	Day	28% 16% 23% 21% 8% 4	490
	11th to 20th	Day	21% 16% 33% 19% 7% 3	450
	21st to end	Day	23% 18% 34% 17% 6% 2	429
November	1st to 10th	Day	21% 18% 33% 17% 9% 2	395
	11th to 20th	Day	26% 25% 28% 15% 5%	400
	21st to end	Day	27% 21% 32% 16% 4 1	400
December	1st to 10th	Day	22% 30% 30% 14% 4	234
	11th to 20th	Day	38% 24% 30% 7% 2	200
	21st to end	Day	25% 27% 29% 14% 3 1	220
January	1st to 10th	Night	22% 23% 40% 13% 3	800
	11th to 20th	Night	29% 22% 34% 14% 2	800
	21st to end	Night	22% 24% 34% 17% 3	880
February	1st to 10th	Night	25% 20% 37% 17% 2	800
	11th to 20th	Night	27% 26% 36% 11% 1	783
	21st to end	Night	28% 23% 33% 14% 2	660
March	1st to 10th	Night	26% 22% 35% 14% 3	800
	11th to 20th	Night	21% 24% 37% 16% 2	800
	21st to end	Night	26% 22% 33% 16% 3	880
April	1st to 10th	Night	25% 22% 35% 16% 2	800
	11th to 20th	Night	26% 20% 34% 17% 3	791
	21st to end	Night	25% 20% 38% 15% 3	620
May	1st to 10th	Night	29% 16% 32% 19% 4	600
	11th to 20th	Night	22% 17% 39% 19% 4	562
	21st to end	Night	20% 8% 39% 27% 6%	433
June	1st to 10th	Night	20% 9% 35% 29% 7%	400
	11th to 20th	Night	20% 9% 37% 31% 4 1	400
	21st to end	Night	17% 6% 35% 35% 6%	400
July	1st to 10th	Night	14% 5% 36% 32% 12%	390
	11th to 20th	Night	16% 6% 30% 36% 13%	388
	21st to end	Night	16% 5% 35% 36% 8%	416
August	1st to 10th	Night	14% 5% 37% 35% 8%	511
	11th to 20th	Night	14% 5% 31% 36% 14%	638
	21st to end	Night	15% 6% 27% 36% 14% 2	836
September	1st to 10th	Night	16% 7% 35% 31% 11% 1	760
	11th to 20th	Night	18% 8% 27% 30% 16% 2	760
	21st to end	Night	22% 8% 30% 28% 10% 2	760
October	1st to 10th	Night	25% 12% 28% 23% 11% 1	760
	11th to 20th	Night	20% 13% 33% 22% 11% 1	760
	21st to end	Night	26% 15% 34% 19% 6%	836
November	1st to 10th	Night	17% 16% 35% 24% 7% 1	780
	11th to 20th	Night	23% 21% 33% 17% 6%	800
	21st to end	Night	25% 20% 32% 19% 5% 1	800
December	1st to 10th	Night	26% 19% 35% 16% 5%	800
	11th to 20th	Night	26% 21% 34% 17% 2	800
	21st to end	Night	25% 20% 37% 16% 2	880

Page generated at 2025-07-18 01:10:01. Version ac07

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