Riverview Farm Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Riverview Farm Park clear sky chart from 2005-11-06 to 2026-04-02.

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	12% 6% 2 6% 4 4 5% 4 6% 8% 43%	131166
	Night	13% 6% 2 6% 4 4 4 3 5% 7% 44%	130656
Transparency	Day	38% 7% 13% 22% 17% 4	134758
	Night	38% 6% 11% 22% 18% 5%	135134
Seeing	Day	17% 11% 27% 26% 15% 5%	17021
	Night	17% 9% 29% 31% 13% 2	26716

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	12% 5% 2 5% 3 3 3 3 4 5% 56%	4978
	11th to 20th	Day	13% 6% 2 5% 3 3 3 2 4 5% 56%	5280
	21st to end	Day	12% 8% 4 7% 4 4 4 3 5% 5% 44%	5780
February	1st to 10th	Day	12% 8% 3 6% 4 6% 4 4 6% 7% 41%	1890
	11th to 20th	Day	21% 7% 2 4 2 3 4 3 4 6% 44%	1991
	21st to end	Day	16% 8% 2 6% 3 5% 5% 4 6% 7% 38%	1730
March	1st to 10th	Day	18% 8% 3 7% 4 3 4 3 4 7% 40%	4901
	11th to 20th	Day	10% 7% 2 6% 4 3 3 3 4 7% 51%	5090
	21st to end	Day	13% 7% 2 5% 4 4 4 3 5% 6% 47%	5741
April	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 6% 50%	2412
	11th to 20th	Day	9% 5% 3 6% 5% 3 4 4 6% 7% 49%	2374
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 7% 44%	2400
May	1st to 10th	Day	12% 8% 3 7% 5% 5% 5% 4 7% 10% 34%	5441
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 9% 32%	6061
	21st to end	Day	13% 6% 2 5% 4 4 4 4 6% 9% 43%	6934
June	1st to 10th	Day	10% 4 2 5% 4 5% 5% 5% 7% 10% 42%	2800
	11th to 20th	Day	10% 6% 2 5% 4 4 4 5% 7% 10% 43%	2800
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 8% 12% 42%	2800
July	1st to 10th	Day	7% 4 2 5% 4 5% 6% 5% 8% 12% 40%	6360
	11th to 20th	Day	10% 7% 3 8% 5% 6% 6% 5% 8% 12% 29%	6000
	21st to end	Day	6% 5% 3 7% 5% 6% 7% 6% 9% 12% 36%	6424
August	1st to 10th	Day	14% 9% 3 8% 5% 5% 6% 5% 7% 10% 27%	4220
	11th to 20th	Day	9% 6% 3 7% 5% 6% 6% 5% 7% 10% 35%	3850
	21st to end	Day	8% 4 2 5% 3 4 5% 4 7% 11% 46%	4312
September	1st to 10th	Day	14% 5% 2 5% 4 4 5% 4 7% 9% 42%	2400
	11th to 20th	Day	15% 7% 3 7% 4 4 5% 4 5% 6% 41%	2400
	21st to end	Day	20% 7% 3 6% 4 5% 4 3 5% 7% 36%	2135
October	1st to 10th	Day	15% 6% 2 5% 4 3 4 3 5% 6% 47%	2000
	11th to 20th	Day	14% 6% 2 5% 3 3 3 2 4 5% 51%	2000
	21st to end	Day	12% 4 3 6% 3 3 4 3 4 6% 52%	2200
November	1st to 10th	Day	13% 5% 1 5% 4 3 4 3 5% 7% 51%	1968
	11th to 20th	Day	13% 6% 2 5% 3 2 3 3 5% 7% 51%	1890
	21st to end	Day	14% 4 2 4 4 3 3 4 4 6% 51%	1806
December	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 5% 54%	2680
	11th to 20th	Day	15% 8% 3 6% 4 3 4 3 5% 4 46%	3070
	21st to end	Day	12% 6% 2 5% 4 3 4 3 5% 7% 49%	4048
January	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 6% 50%	7900
	11th to 20th	Night	12% 6% 2 6% 3 3 3 2 4 4 54%	7680
	21st to end	Night	15% 7% 2 6% 4 3 3 2 4 6% 48%	8401
February	1st to 10th	Night	16% 7% 2 6% 4 3 4 3 5% 6% 43%	2730
	11th to 20th	Night	21% 7% 2 5% 4 3 4 3 5% 5% 40%	2513
	21st to end	Night	16% 8% 2 6% 3 4 4 2 4 6% 46%	2076
March	1st to 10th	Night	18% 7% 2 6% 4 3 3 3 4 5% 44%	5168
	11th to 20th	Night	12% 6% 3 6% 4 3 4 3 4 6% 49%	5090
	21st to end	Night	14% 7% 3 6% 4 4 4 3 5% 5% 47%	5431
April	1st to 10th	Night	12% 7% 2 6% 5% 4 4 4 6% 7% 42%	2011
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 5% 7% 49%	1975
	21st to end	Night	13% 7% 2 5% 4 3 4 4 6% 7% 45%	2000
May	1st to 10th	Night	12% 9% 3 8% 5% 5% 6% 4 7% 9% 31%	4490
	11th to 20th	Night	19% 9% 2 8% 5% 4 4 4 6% 7% 32%	3823
	21st to end	Night	15% 7% 3 6% 5% 4 4 4 5% 9% 38%	3920
June	1st to 10th	Night	11% 5% 2 4 6% 6% 4 5% 7% 10% 40%	1600
	11th to 20th	Night	9% 6% 2 6% 5% 5% 5% 5% 8% 9% 41%	1600
	21st to end	Night	7% 5% 2 6% 6% 5% 6% 5% 6% 8% 44%	1600
July	1st to 10th	Night	8% 5% 2 7% 5% 6% 5% 5% 8% 12% 37%	3598
	11th to 20th	Night	10% 7% 3 8% 5% 5% 6% 6% 9% 12% 30%	3953
	21st to end	Night	10% 7% 3 7% 5% 5% 6% 5% 7% 9% 35%	4427
August	1st to 10th	Night	18% 8% 3 7% 4 5% 5% 5% 7% 10% 29%	2915
	11th to 20th	Night	9% 7% 3 8% 5% 5% 5% 4 6% 8% 40%	3166
	21st to end	Night	9% 5% 2 5% 4 5% 5% 3 7% 10% 45%	3586
September	1st to 10th	Night	12% 4 2 5% 4 4 4 4 7% 9% 45%	2000
	11th to 20th	Night	12% 7% 3 7% 4 4 4 4 5% 7% 44%	2000
	21st to end	Night	19% 8% 3 7% 4 5% 4 3 4 7% 35%	2261
October	1st to 10th	Night	15% 6% 2 5% 4 4 4 3 4 6% 48%	2400
	11th to 20th	Night	15% 6% 2 4 3 3 3 3 5% 5% 50%	2400
	21st to end	Night	14% 5% 2 4 4 3 3 3 5% 6% 51%	2640
November	1st to 10th	Night	14% 6% 2 6% 3 3 3 3 4 5% 50%	2548
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 5% 6% 48%	2730
	21st to end	Night	11% 5% 1 6% 4 3 4 3 6% 6% 51%	2809
December	1st to 10th	Night	11% 5% 2 6% 3 3 4 3 4 6% 54%	4720
	11th to 20th	Night	17% 8% 2 7% 5% 4 5% 4 4 6% 40%	5345
	21st to end	Night	11% 6% 2 6% 3 3 4 3 5% 7% 48%	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	32% 3 11% 25% 19% 10%	4979
	11th to 20th	Day	33% 3 4 16% 34% 9%	5280
	21st to end	Day	42% 4 7% 26% 17% 3	5780
February	1st to 10th	Day	41% 5% 12% 24% 15% 3	1890
	11th to 20th	Day	43% 4 9% 19% 20% 5%	2000
	21st to end	Day	44% 5% 11% 18% 18% 5%	1730
March	1st to 10th	Day	45% 5% 8% 18% 17% 7%	4901
	11th to 20th	Day	34% 5% 9% 20% 24% 9%	5090
	21st to end	Day	37% 6% 14% 19% 20% 5%	5741
April	1st to 10th	Day	33% 6% 12% 22% 21% 6%	2412
	11th to 20th	Day	32% 7% 12% 24% 19% 6%	2374
	21st to end	Day	38% 7% 12% 21% 17% 4	2400
May	1st to 10th	Day	44% 9% 17% 18% 11% 1	5473
	11th to 20th	Day	47% 8% 15% 19% 9% 1	6065
	21st to end	Day	36% 8% 15% 24% 15% 2	6949
June	1st to 10th	Day	34% 10% 15% 24% 15% 1	2800
	11th to 20th	Day	34% 9% 18% 23% 14% 1	2800
	21st to end	Day	33% 10% 17% 25% 14% 1	2800
July	1st to 10th	Day	35% 10% 20% 22% 11% 2	6290
	11th to 20th	Day	45% 11% 25% 15% 3 1	5928
	21st to end	Day	39% 10% 15% 23% 13% 1	6240
August	1st to 10th	Day	52% 8% 17% 18% 4	4207
	11th to 20th	Day	42% 8% 14% 24% 12%	3886
	21st to end	Day	32% 9% 14% 27% 16% 2	4312
September	1st to 10th	Day	38% 10% 16% 17% 16% 4	2400
	11th to 20th	Day	43% 6% 11% 21% 17% 2	2400
	21st to end	Day	47% 7% 10% 19% 14% 2	2135
October	1st to 10th	Day	32% 5% 9% 25% 26% 3	3260
	11th to 20th	Day	26% 4 6% 19% 38% 8%	3240
	21st to end	Day	23% 3 8% 27% 26% 12%	3538
November	1st to 10th	Day	35% 5% 9% 26% 21% 4	1968
	11th to 20th	Day	34% 4 12% 23% 22% 6%	1890
	21st to end	Day	35% 4 8% 26% 22% 5%	1806
December	1st to 10th	Day	34% 4 9% 28% 22% 4	2680
	11th to 20th	Day	42% 4 13% 20% 16% 5%	3066
	21st to end	Day	34% 4 14% 29% 18% 1	4048
January	1st to 10th	Night	35% 4 11% 22% 21% 7%	7901
	11th to 20th	Night	35% 4 4 19% 30% 8%	7680
	21st to end	Night	40% 3 6% 25% 20% 6%	8401
February	1st to 10th	Night	42% 5% 10% 22% 17% 4	2730
	11th to 20th	Night	46% 4 7% 21% 17% 5%	2515
	21st to end	Night	41% 5% 7% 22% 18% 7%	2076
March	1st to 10th	Night	43% 5% 9% 18% 18% 8%	5168
	11th to 20th	Night	37% 5% 8% 19% 22% 10%	5090
	21st to end	Night	39% 5% 10% 24% 17% 6%	5431
April	1st to 10th	Night	38% 7% 12% 17% 22% 5%	2011
	11th to 20th	Night	34% 5% 12% 23% 20% 6%	1975
	21st to end	Night	37% 6% 12% 24% 18% 3	2000
May	1st to 10th	Night	46% 9% 16% 17% 10% 1	4520
	11th to 20th	Night	49% 9% 12% 22% 8% 1	3824
	21st to end	Night	42% 8% 14% 23% 11% 1	3927
June	1st to 10th	Night	34% 10% 17% 23% 14% 1	1600
	11th to 20th	Night	36% 10% 18% 21% 14% 1	1600
	21st to end	Night	33% 11% 14% 25% 15% 2	1600
July	1st to 10th	Night	39% 10% 17% 22% 10% 2	3560
	11th to 20th	Night	43% 12% 25% 16% 4 1	3905
	21st to end	Night	43% 9% 13% 21% 15%	4297
August	1st to 10th	Night	50% 8% 19% 19% 4	2904
	11th to 20th	Night	41% 7% 18% 22% 13%	3196
	21st to end	Night	33% 7% 12% 26% 21% 2	3586
September	1st to 10th	Night	36% 8% 17% 21% 15% 4	2000
	11th to 20th	Night	40% 6% 11% 20% 20% 3	2000
	21st to end	Night	49% 7% 11% 17% 15% 2	2261
October	1st to 10th	Night	37% 5% 9% 22% 25% 3	3920
	11th to 20th	Night	27% 4 6% 20% 34% 10%	3899
	21st to end	Night	22% 4 7% 30% 25% 12%	4252
November	1st to 10th	Night	36% 4 9% 22% 24% 4	2548
	11th to 20th	Night	37% 5% 9% 20% 20% 9%	2730
	21st to end	Night	34% 5% 9% 25% 22% 5%	2809
December	1st to 10th	Night	33% 4 7% 26% 25% 5%	4720
	11th to 20th	Night	47% 4 11% 17% 15% 6%	5348
	21st to end	Night	35% 6% 14% 27% 16% 2	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	19% 22% 40% 13% 6%	278
	11th to 20th	Day	24% 21% 35% 18% 2	330
	21st to end	Day	20% 21% 37% 20% 2	363
February	1st to 10th	Day	18% 19% 41% 15% 6%	330
	11th to 20th	Day	28% 23% 31% 15% 3	479
	21st to end	Day	22% 20% 35% 18% 4	446
March	1st to 10th	Day	19% 19% 38% 17% 7%	540
	11th to 20th	Day	22% 20% 32% 20% 4 1	540
	21st to end	Day	19% 18% 37% 21% 6% 1	594
April	1st to 10th	Day	20% 17% 39% 16% 7% 1	504
	11th to 20th	Day	14% 16% 37% 20% 10% 3	492
	21st to end	Day	16% 14% 34% 24% 10% 2	500
May	1st to 10th	Day	15% 17% 35% 22% 11% 1	503
	11th to 20th	Day	19% 9% 31% 28% 11% 2	527
	21st to end	Day	18% 6% 25% 28% 19% 4	573
June	1st to 10th	Day	13% 4 23% 34% 21% 6%	530
	11th to 20th	Day	12% 6% 19% 32% 22% 8%	530
	21st to end	Day	9% 4 19% 34% 25% 10%	530
July	1st to 10th	Day	10% 2 13% 34% 31% 10%	525
	11th to 20th	Day	8% 2 11% 36% 31% 12%	524
	21st to end	Day	9% 2 17% 35% 28% 11%	576
August	1st to 10th	Day	14% 3 18% 32% 25% 8%	526
	11th to 20th	Day	12% 4 12% 31% 29% 11%	519
	21st to end	Day	11% 3 14% 32% 28% 12%	583
September	1st to 10th	Day	15% 2 21% 28% 20% 14%	530
	11th to 20th	Day	18% 4 18% 30% 20% 11%	530
	21st to end	Day	26% 8% 22% 25% 15% 5%	530
October	1st to 10th	Day	20% 5% 19% 25% 20% 10%	530
	11th to 20th	Day	16% 11% 29% 24% 18% 3	530
	21st to end	Day	15% 10% 33% 25% 13% 5%	583
November	1st to 10th	Day	19% 9% 28% 26% 15% 4	488
	11th to 20th	Day	18% 16% 31% 24% 10% 1	430
	21st to end	Day	17% 15% 28% 25% 12% 2	346
December	1st to 10th	Day	20% 16% 38% 20% 5% 1	220
	11th to 20th	Day	20% 11% 35% 27% 7%	220
	21st to end	Day	20% 17% 31% 24% 8%	242
January	1st to 10th	Night	17% 18% 38% 22% 4	840
	11th to 20th	Night	20% 14% 38% 23% 4	840
	21st to end	Night	20% 13% 40% 26% 2	924
February	1st to 10th	Night	20% 13% 42% 24% 3	840
	11th to 20th	Night	25% 18% 38% 18% 1	823
	21st to end	Night	19% 18% 39% 22% 3	692
March	1st to 10th	Night	18% 14% 37% 26% 5%	840
	11th to 20th	Night	20% 15% 37% 23% 5%	840
	21st to end	Night	20% 13% 38% 24% 5%	924
April	1st to 10th	Night	17% 16% 41% 22% 4	805
	11th to 20th	Night	16% 11% 40% 24% 9% 1	791
	21st to end	Night	16% 9% 35% 32% 7%	800
May	1st to 10th	Night	16% 12% 35% 31% 5% 1	800
	11th to 20th	Night	16% 5% 29% 39% 10% 1	512
	21st to end	Night	14% 5% 18% 44% 17% 1	433
June	1st to 10th	Night	13% 3 21% 45% 17% 2	400
	11th to 20th	Night	10% 3 21% 41% 24% 2	400
	21st to end	Night	7% 2 20% 45% 25% 2	400
July	1st to 10th	Night	8% 2 17% 46% 25% 2	390
	11th to 20th	Night	8% 2 10% 41% 33% 5%	533
	21st to end	Night	10% 2 16% 43% 26% 3	657
August	1st to 10th	Night	11% 2 14% 41% 29% 3	597
	11th to 20th	Night	12% 3 13% 41% 27% 4	771
	21st to end	Night	12% 3 12% 36% 32% 5%	880
September	1st to 10th	Night	15% 3 15% 38% 25% 6%	800
	11th to 20th	Night	18% 3 15% 34% 26% 5%	800
	21st to end	Night	24% 5% 18% 32% 20% 2	800
October	1st to 10th	Night	18% 5% 18% 31% 24% 5%	800
	11th to 20th	Night	21% 8% 26% 29% 16% 2	800
	21st to end	Night	16% 8% 28% 29% 16% 3	880
November	1st to 10th	Night	18% 7% 28% 29% 16% 2	820
	11th to 20th	Night	17% 11% 32% 30% 9%	840
	21st to end	Night	14% 11% 31% 32% 12% 1	840
December	1st to 10th	Night	20% 11% 34% 26% 8%	840
	11th to 20th	Night	18% 10% 37% 29% 6%	840
	21st to end	Night	17% 12% 33% 32% 6%	924

Page generated at 2026-03-30 02:18:44. Version ac07

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