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 2024-07-08.

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% 6% 2 6% 4 4 4 4 6% 8% 43%	89616
	Night	14% 7% 2 6% 4 4 4 3 5% 7% 43%	89670
Transparency	Day	38% 8% 12% 22% 16% 3	89378
	Night	39% 7% 11% 22% 17% 4	89512
Seeing	Day	17% 12% 28% 25% 14% 4	14767
	Night	17% 10% 29% 30% 13% 2	24376

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	17% 6% 2 4 3 2 3 3 4 4 52%	2680
	11th to 20th	Day	13% 7% 3 6% 4 4 4 3 5% 7% 47%	2840
	21st to end	Day	13% 9% 4 8% 4 4 3 3 5% 5% 41%	3124
February	1st to 10th	Day	13% 9% 3 5% 4 6% 4 4 6% 7% 40%	1710
	11th to 20th	Day	20% 6% 2 4 2 3 4 3 4 6% 46%	1796
	21st to end	Day	16% 8% 2 6% 3 5% 5% 5% 6% 7% 37%	1570
March	1st to 10th	Day	21% 9% 4 7% 4 3 4 3 4 6% 36%	3336
	11th to 20th	Day	10% 5% 2 4 3 4 3 3 4 7% 55%	3480
	21st to end	Day	18% 8% 2 5% 4 4 4 3 5% 6% 43%	3925
April	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 6% 51%	2280
	11th to 20th	Day	9% 5% 2 6% 5% 3 4 5% 5% 7% 49%	2254
	21st to end	Day	14% 6% 2 6% 4 4 4 3 6% 7% 44%	2280
May	1st to 10th	Day	13% 8% 3 8% 5% 5% 5% 4 6% 10% 33%	3787
	11th to 20th	Day	18% 8% 3 7% 5% 5% 5% 4 5% 8% 33%	4225
	21st to end	Day	9% 5% 2 5% 3 4 4 5% 7% 10% 48%	4823
June	1st to 10th	Day	10% 4 2 5% 4 5% 5% 6% 7% 10% 42%	2660
	11th to 20th	Day	10% 5% 2 5% 4 5% 4 5% 8% 10% 43%	2660
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 8% 12% 41%	2660
July	1st to 10th	Day	7% 4 2 5% 5% 5% 6% 5% 8% 12% 41%	2621
	11th to 20th	Day	6% 5% 2 5% 5% 5% 5% 6% 9% 13% 40%	2384
	21st to end	Day	6% 4 2 6% 5% 6% 7% 7% 10% 11% 36%	2547
August	1st to 10th	Day	9% 6% 2 6% 5% 6% 6% 5% 8% 10% 36%	2326
	11th to 20th	Day	10% 7% 2 7% 6% 6% 6% 5% 7% 9% 35%	2126
	21st to end	Day	9% 5% 3 7% 4 4 5% 4 7% 11% 40%	2376
September	1st to 10th	Day	14% 5% 2 5% 4 4 4 4 7% 9% 41%	2160
	11th to 20th	Day	13% 6% 3 7% 4 4 5% 4 5% 6% 43%	2160
	21st to end	Day	19% 7% 3 6% 4 5% 4 3 5% 7% 37%	1923
October	1st to 10th	Day	16% 7% 2 5% 4 3 3 3 5% 6% 46%	1800
	11th to 20th	Day	14% 7% 2 5% 4 3 3 3 4 6% 50%	1800
	21st to end	Day	12% 5% 3 6% 3 3 4 3 4 6% 50%	1980
November	1st to 10th	Day	14% 5% 1 5% 4 2 4 2 5% 7% 51%	1777
	11th to 20th	Day	14% 6% 2 4 4 2 3 3 5% 6% 51%	1710
	21st to end	Day	15% 5% 2 4 3 3 3 4 4 6% 51%	1634
December	1st to 10th	Day	16% 6% 3 5% 4 4 3 4 6% 7% 43%	1520
	11th to 20th	Day	15% 6% 2 4 3 3 3 3 4 4 53%	1910
	21st to end	Day	15% 7% 2 5% 4 4 4 3 6% 6% 44%	2772
January	1st to 10th	Night	13% 7% 2 7% 4 3 4 3 4 6% 47%	4264
	11th to 20th	Night	15% 8% 3 6% 4 3 4 3 5% 5% 43%	4120
	21st to end	Night	17% 8% 2 7% 4 3 3 2 5% 5% 43%	4532
February	1st to 10th	Night	16% 7% 2 6% 4 4 4 3 6% 6% 42%	2470
	11th to 20th	Night	20% 7% 3 6% 4 3 3 3 5% 6% 41%	2269
	21st to end	Night	17% 8% 2 6% 3 4 3 2 4 6% 46%	1884
March	1st to 10th	Night	23% 9% 3 7% 4 4 3 3 5% 5% 34%	3513
	11th to 20th	Night	14% 6% 2 5% 4 3 4 3 4 6% 50%	3480
	21st to end	Night	17% 8% 3 6% 4 3 3 2 3 4 47%	3705
April	1st to 10th	Night	12% 7% 2 6% 5% 4 4 4 6% 7% 42%	1900
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 7% 50%	1875
	21st to end	Night	14% 7% 2 5% 4 3 4 4 6% 7% 45%	1900
May	1st to 10th	Night	15% 9% 3 8% 6% 5% 5% 4 6% 8% 32%	3130
	11th to 20th	Night	19% 8% 2 7% 5% 4 4 4 6% 7% 33%	2673
	21st to end	Night	10% 5% 2 6% 5% 4 4 4 5% 9% 44%	2732
June	1st to 10th	Night	11% 5% 2 4 5% 6% 4 5% 7% 10% 40%	1520
	11th to 20th	Night	8% 6% 2 6% 4 5% 6% 4 8% 9% 42%	1520
	21st to end	Night	7% 6% 2 6% 7% 5% 5% 5% 6% 8% 43%	1520
July	1st to 10th	Night	8% 5% 2 7% 6% 5% 5% 3 7% 11% 41%	1504
	11th to 20th	Night	6% 4 2 6% 5% 5% 5% 5% 9% 11% 42%	1572
	21st to end	Night	7% 6% 3 6% 5% 5% 5% 5% 9% 11% 37%	1771
August	1st to 10th	Night	7% 5% 2 7% 5% 6% 7% 5% 8% 10% 37%	1611
	11th to 20th	Night	9% 6% 3 9% 5% 5% 5% 4 7% 9% 38%	1757
	21st to end	Night	9% 5% 3 6% 5% 6% 6% 4 8% 11% 38%	1980
September	1st to 10th	Night	13% 4 2 5% 4 4 4 4 7% 9% 44%	1800
	11th to 20th	Night	11% 7% 3 6% 4 4 4 4 5% 8% 45%	1800
	21st to end	Night	18% 8% 3 7% 4 5% 4 3 4 7% 37%	2033
October	1st to 10th	Night	15% 6% 2 5% 4 4 3 3 4 6% 47%	2160
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 5% 6% 49%	2160
	21st to end	Night	14% 5% 2 4 4 3 3 3 5% 6% 50%	2376
November	1st to 10th	Night	15% 6% 2 6% 3 3 4 3 4 5% 50%	2299
	11th to 20th	Night	15% 5% 2 6% 4 3 3 3 4 6% 48%	2470
	21st to end	Night	12% 5% 1 5% 4 3 4 3 6% 6% 50%	2541
December	1st to 10th	Night	17% 7% 3 7% 4 4 4 3 5% 5% 41%	2660
	11th to 20th	Night	17% 6% 2 5% 3 3 4 3 5% 6% 47%	3285
	21st to end	Night	14% 7% 2 6% 4 4 4 4 5% 6% 44%	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	35% 5% 6% 30% 21% 3	2681
	11th to 20th	Day	37% 5% 8% 19% 26% 5%	2840
	21st to end	Day	44% 6% 10% 20% 18% 3	3124
February	1st to 10th	Day	41% 5% 11% 25% 14% 3	1710
	11th to 20th	Day	41% 5% 9% 20% 20% 6%	1805
	21st to end	Day	44% 6% 12% 16% 17% 5%	1570
March	1st to 10th	Day	48% 6% 10% 16% 15% 5%	3336
	11th to 20th	Day	30% 6% 9% 22% 24% 8%	3480
	21st to end	Day	41% 8% 13% 18% 18% 3	3925
April	1st to 10th	Day	33% 6% 11% 22% 22% 6%	2280
	11th to 20th	Day	32% 7% 12% 24% 20% 6%	2254
	21st to end	Day	38% 7% 12% 22% 17% 5%	2280
May	1st to 10th	Day	44% 11% 15% 19% 9% 2	3822
	11th to 20th	Day	47% 10% 12% 22% 8% 1	4229
	21st to end	Day	29% 10% 17% 25% 17% 2	4837
June	1st to 10th	Day	34% 11% 15% 24% 15% 1	2660
	11th to 20th	Day	33% 10% 17% 24% 14% 2	2660
	21st to end	Day	34% 10% 17% 23% 14% 1	2660
July	1st to 10th	Day	34% 13% 16% 22% 12% 3	2551
	11th to 20th	Day	33% 13% 21% 23% 9% 2	2312
	21st to end	Day	36% 13% 18% 20% 12% 1	2405
August	1st to 10th	Day	41% 11% 17% 23% 7% 1	2313
	11th to 20th	Day	42% 11% 14% 21% 11% 1	2126
	21st to end	Day	37% 12% 16% 19% 13% 3	2376
September	1st to 10th	Day	38% 10% 17% 16% 16% 4	2160
	11th to 20th	Day	41% 7% 11% 21% 18% 2	2160
	21st to end	Day	46% 7% 9% 20% 15% 2	1923
October	1st to 10th	Day	40% 6% 9% 22% 20% 3	1800
	11th to 20th	Day	37% 5% 7% 26% 21% 5%	1800
	21st to end	Day	36% 5% 7% 22% 24% 7%	1980
November	1st to 10th	Day	35% 5% 9% 25% 21% 4	1777
	11th to 20th	Day	35% 4 12% 21% 22% 6%	1710
	21st to end	Day	35% 5% 8% 26% 21% 5%	1634
December	1st to 10th	Day	41% 6% 12% 21% 17% 3	1520
	11th to 20th	Day	35% 4 8% 28% 17% 7%	1906
	21st to end	Day	40% 5% 11% 27% 16% 2	2772
January	1st to 10th	Night	37% 5% 8% 24% 20% 5%	4264
	11th to 20th	Night	43% 6% 7% 20% 21% 3	4120
	21st to end	Night	44% 5% 7% 19% 19% 6%	4532
February	1st to 10th	Night	41% 5% 10% 23% 17% 4	2470
	11th to 20th	Night	45% 4 7% 21% 17% 6%	2271
	21st to end	Night	41% 5% 7% 22% 19% 7%	1884
March	1st to 10th	Night	51% 6% 9% 17% 14% 2	3513
	11th to 20th	Night	35% 5% 8% 19% 24% 9%	3480
	21st to end	Night	40% 5% 8% 25% 17% 5%	3705
April	1st to 10th	Night	38% 7% 11% 17% 22% 5%	1900
	11th to 20th	Night	34% 5% 11% 23% 21% 6%	1875
	21st to end	Night	37% 6% 12% 24% 17% 3	1900
May	1st to 10th	Night	46% 11% 14% 19% 10% 1	3160
	11th to 20th	Night	45% 11% 12% 23% 7% 1	2674
	21st to end	Night	33% 11% 17% 24% 13% 1	2739
June	1st to 10th	Night	34% 10% 18% 24% 14% 1	1520
	11th to 20th	Night	35% 10% 18% 22% 14% 1	1520
	21st to end	Night	34% 11% 15% 23% 15% 2	1520
July	1st to 10th	Night	36% 12% 15% 23% 11% 3	1464
	11th to 20th	Night	29% 12% 20% 27% 9% 2	1521
	21st to end	Night	34% 13% 17% 24% 12%	1672
August	1st to 10th	Night	37% 13% 22% 21% 7%	1600
	11th to 20th	Night	41% 10% 19% 19% 11%	1757
	21st to end	Night	38% 11% 18% 21% 11% 2	1980
September	1st to 10th	Night	36% 8% 18% 20% 15% 4	1800
	11th to 20th	Night	39% 7% 11% 21% 20% 3	1800
	21st to end	Night	47% 7% 10% 17% 16% 2	2033
October	1st to 10th	Night	38% 6% 8% 22% 22% 3	2160
	11th to 20th	Night	37% 5% 8% 23% 23% 5%	2160
	21st to end	Night	35% 5% 9% 22% 23% 7%	2376
November	1st to 10th	Night	37% 5% 10% 22% 23% 4	2299
	11th to 20th	Night	37% 5% 9% 19% 21% 9%	2470
	21st to end	Night	34% 5% 9% 25% 22% 5%	2541
December	1st to 10th	Night	45% 6% 9% 21% 16% 3	2660
	11th to 20th	Night	38% 5% 11% 21% 20% 6%	3288
	21st to end	Night	38% 6% 13% 23% 18% 2	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	22% 24% 37% 10% 7%	227
	11th to 20th	Day	26% 25% 34% 13% 2	270
	21st to end	Day	21% 24% 37% 15% 2	297
February	1st to 10th	Day	19% 22% 41% 12% 5%	270
	11th to 20th	Day	28% 26% 31% 13% 2	404
	21st to end	Day	23% 23% 36% 15% 3	382
March	1st to 10th	Day	20% 21% 39% 15% 5%	460
	11th to 20th	Day	23% 23% 32% 17% 4 1	460
	21st to end	Day	21% 20% 37% 16% 5% 1	506
April	1st to 10th	Day	20% 18% 40% 14% 6% 1	460
	11th to 20th	Day	14% 17% 38% 18% 10% 3	452
	21st to end	Day	18% 15% 35% 24% 7% 2	460
May	1st to 10th	Day	15% 18% 35% 20% 11% 1	463
	11th to 20th	Day	19% 9% 32% 28% 11% 1	487
	21st to end	Day	18% 6% 25% 28% 20% 4	529
June	1st to 10th	Day	13% 3 24% 33% 21% 5%	490
	11th to 20th	Day	12% 7% 20% 33% 21% 8%	490
	21st to end	Day	9% 4 21% 36% 23% 7%	490
July	1st to 10th	Day	9% 2 14% 37% 30% 8%	474
	11th to 20th	Day	6% 3 13% 39% 30% 9%	444
	21st to end	Day	10% 1 19% 37% 26% 7%	488
August	1st to 10th	Day	11% 3 19% 35% 24% 9%	446
	11th to 20th	Day	13% 4 14% 31% 28% 11%	439
	21st to end	Day	12% 3 15% 31% 26% 12%	495
September	1st to 10th	Day	14% 3 22% 28% 19% 14%	450
	11th to 20th	Day	16% 4 18% 32% 20% 12%	450
	21st to end	Day	24% 9% 24% 25% 13% 5%	450
October	1st to 10th	Day	21% 6% 21% 25% 20% 7%	450
	11th to 20th	Day	15% 12% 28% 25% 17% 2	450
	21st to end	Day	15% 12% 33% 25% 11% 4	495
November	1st to 10th	Day	19% 10% 30% 23% 14% 4	417
	11th to 20th	Day	18% 18% 31% 22% 9% 1	370
	21st to end	Day	19% 17% 27% 23% 12% 2	294
December	1st to 10th	Day	21% 19% 41% 14% 4 1	180
	11th to 20th	Day	19% 13% 38% 22% 7%	180
	21st to end	Day	23% 20% 28% 19% 9% 1	198
January	1st to 10th	Night	18% 19% 36% 23% 4	760
	11th to 20th	Night	21% 15% 36% 24% 5%	760
	21st to end	Night	20% 14% 39% 25% 2	836
February	1st to 10th	Night	19% 13% 42% 23% 3	760
	11th to 20th	Night	24% 19% 39% 16% 1	743
	21st to end	Night	20% 19% 38% 21% 3	628
March	1st to 10th	Night	18% 15% 37% 25% 5%	760
	11th to 20th	Night	21% 15% 38% 21% 5%	760
	21st to end	Night	20% 14% 38% 23% 5%	836
April	1st to 10th	Night	18% 16% 41% 21% 4	760
	11th to 20th	Night	15% 12% 40% 23% 9% 1	751
	21st to end	Night	17% 10% 37% 31% 6%	760
May	1st to 10th	Night	16% 12% 36% 30% 5% 1	760
	11th to 20th	Night	15% 5% 30% 39% 9% 1	487
	21st to end	Night	14% 4 18% 44% 18% 1	411
June	1st to 10th	Night	12% 3 22% 44% 17% 2	380
	11th to 20th	Night	9% 3 22% 41% 23% 2	380
	21st to end	Night	7% 2 21% 46% 23% 1	380
July	1st to 10th	Night	9% 2 17% 46% 23% 2	366
	11th to 20th	Night	8% 1 12% 43% 32% 4	477
	21st to end	Night	9% 2 17% 45% 25% 2	591
August	1st to 10th	Night	9% 1 14% 43% 28% 3	537
	11th to 20th	Night	12% 2 14% 41% 26% 4	693
	21st to end	Night	13% 3 13% 35% 32% 5%	792
September	1st to 10th	Night	15% 3 14% 36% 26% 6%	720
	11th to 20th	Night	16% 3 15% 35% 27% 5%	720
	21st to end	Night	23% 5% 19% 31% 20% 2	720
October	1st to 10th	Night	18% 5% 19% 31% 23% 4	720
	11th to 20th	Night	20% 8% 25% 29% 16% 2	720
	21st to end	Night	16% 9% 29% 29% 15% 2	792
November	1st to 10th	Night	18% 7% 29% 27% 16% 3	740
	11th to 20th	Night	17% 12% 32% 29% 10% 1	760
	21st to end	Night	15% 12% 30% 31% 12% 1	760
December	1st to 10th	Night	21% 12% 35% 24% 8% 1	760
	11th to 20th	Night	19% 10% 37% 28% 6%	760
	21st to end	Night	18% 12% 33% 30% 6%	836

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