Riverbend Recreation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Riverbend Recreation Area clear sky chart from 2005-11-06 to 2026-06-01.

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	14% 10% 4 9% 5% 5% 5% 4 5% 7% 32%	132214
	Night	15% 11% 4 9% 5% 4 4 4 5% 6% 33%	131018
Transparency	Day	49% 6% 11% 20% 12% 1	135826
	Night	49% 5% 11% 20% 13% 1	135476
Seeing	Day	18% 11% 27% 23% 15% 6%	17574
	Night	20% 9% 28% 29% 13% 1	27387

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	16% 18% 7% 15% 7% 5% 4 3 5% 5% 14%	4691
	11th to 20th	Day	12% 17% 6% 15% 9% 6% 6% 3 3 3 19%	4968
	21st to end	Day	19% 15% 7% 13% 7% 7% 6% 3 4 4 15%	5780
February	1st to 10th	Day	16% 15% 6% 12% 7% 7% 4 3 4 5% 22%	1890
	11th to 20th	Day	14% 13% 6% 13% 8% 5% 5% 4 4 5% 24%	2040
	21st to end	Day	16% 15% 4 10% 4 5% 4 3 6% 7% 26%	1730
March	1st to 10th	Day	18% 14% 7% 12% 5% 5% 4 2 4 5% 25%	4707
	11th to 20th	Day	11% 11% 3 8% 4 5% 4 4 5% 7% 38%	5090
	21st to end	Day	18% 13% 4 11% 5% 5% 4 4 5% 6% 25%	5586
April	1st to 10th	Day	15% 12% 4 9% 6% 5% 5% 4 6% 6% 29%	2431
	11th to 20th	Day	17% 9% 3 7% 5% 5% 5% 4 6% 7% 34%	2634
	21st to end	Day	19% 8% 2 7% 5% 4 4 4 4 7% 34%	2730
May	1st to 10th	Day	22% 9% 3 7% 5% 5% 5% 4 5% 7% 28%	5992
	11th to 20th	Day	17% 7% 3 6% 5% 5% 5% 4 6% 7% 35%	5991
	21st to end	Day	16% 6% 2 7% 5% 4 5% 4 6% 7% 39%	6576
June	1st to 10th	Day	13% 6% 3 6% 5% 5% 4 4 7% 8% 39%	2669
	11th to 20th	Day	11% 6% 2 6% 5% 5% 6% 5% 6% 8% 40%	2800
	21st to end	Day	10% 5% 2 6% 6% 5% 6% 6% 8% 9% 39%	2800
July	1st to 10th	Day	8% 6% 2 7% 5% 5% 5% 4 7% 11% 40%	6360
	11th to 20th	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	6235
	21st to end	Day	9% 5% 2 8% 5% 5% 5% 5% 7% 10% 39%	6424
August	1st to 10th	Day	9% 5% 3 6% 5% 5% 5% 4 7% 9% 42%	4234
	11th to 20th	Day	8% 5% 2 6% 5% 6% 5% 5% 9% 12% 38%	4174
	21st to end	Day	8% 5% 3 6% 5% 4 5% 4 7% 10% 44%	4549
September	1st to 10th	Day	13% 5% 2 5% 4 4 4 3 6% 8% 47%	2250
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 5% 9% 48%	2200
	21st to end	Day	17% 7% 2 6% 4 4 3 2 5% 7% 42%	2200
October	1st to 10th	Day	13% 6% 3 7% 4 4 3 4 5% 7% 44%	2166
	11th to 20th	Day	16% 7% 3 6% 4 5% 4 4 5% 6% 40%	2000
	21st to end	Day	19% 9% 3 7% 5% 5% 5% 3 6% 7% 31%	2065
November	1st to 10th	Day	12% 8% 2 7% 4 4 4 4 5% 7% 43%	1852
	11th to 20th	Day	17% 14% 4 7% 5% 4 4 3 4 5% 34%	1890
	21st to end	Day	18% 16% 5% 8% 5% 4 4 3 4 6% 27%	1890
December	1st to 10th	Day	15% 15% 7% 14% 6% 5% 4 3 4 5% 23%	3020
	11th to 20th	Day	18% 17% 7% 11% 5% 4 4 3 4 5% 21%	3463
	21st to end	Day	25% 21% 7% 12% 5% 4 4 2 3 4 13%	4137
January	1st to 10th	Night	15% 17% 7% 15% 7% 5% 5% 3 4 4 19%	8232
	11th to 20th	Night	10% 18% 8% 16% 7% 6% 6% 4 4 5% 17%	8003
	21st to end	Night	18% 13% 6% 10% 5% 5% 5% 4 5% 6% 23%	8401
February	1st to 10th	Night	18% 14% 5% 11% 6% 5% 4 4 5% 5% 24%	2730
	11th to 20th	Night	15% 13% 5% 11% 6% 6% 5% 4 5% 5% 26%	2463
	21st to end	Night	20% 14% 4 9% 6% 4 3 3 4 6% 27%	2076
March	1st to 10th	Night	17% 13% 4 8% 5% 4 4 2 4 5% 35%	5365
	11th to 20th	Night	11% 6% 2 6% 5% 5% 5% 5% 6% 7% 42%	5090
	21st to end	Night	17% 9% 4 8% 5% 4 4 3 5% 6% 36%	5588
April	1st to 10th	Night	17% 10% 3 8% 5% 5% 4 4 5% 6% 34%	2206
	11th to 20th	Night	16% 8% 2 7% 4 6% 5% 4 6% 7% 36%	1935
	21st to end	Night	16% 9% 3 7% 4 4 5% 3 5% 7% 37%	1890
May	1st to 10th	Night	21% 9% 4 9% 5% 6% 5% 3 5% 5% 28%	4123
	11th to 20th	Night	17% 7% 3 7% 4 4 4 4 6% 9% 38%	4122
	21st to end	Night	14% 6% 2 6% 4 4 5% 3 6% 8% 42%	4520
June	1st to 10th	Night	11% 6% 2 6% 4 4 4 5% 6% 8% 45%	1727
	11th to 20th	Night	8% 5% 2 6% 4 5% 5% 4 7% 9% 45%	1600
	21st to end	Night	9% 4 2 5% 4 5% 4 4 7% 9% 46%	1600
July	1st to 10th	Night	9% 4 2 5% 5% 5% 4 4 6% 10% 45%	3618
	11th to 20th	Night	8% 4 2 6% 4 5% 5% 4 7% 9% 46%	3721
	21st to end	Night	9% 6% 2 7% 4 5% 4 4 6% 8% 45%	4427
August	1st to 10th	Night	11% 6% 2 6% 5% 4 4 4 6% 9% 41%	2915
	11th to 20th	Night	8% 6% 3 6% 4 4 4 4 6% 9% 46%	2875
	21st to end	Night	6% 5% 2 6% 4 5% 5% 4 6% 9% 48%	3345
September	1st to 10th	Night	11% 5% 2 5% 4 3 4 2 5% 7% 52%	2128
	11th to 20th	Night	10% 5% 2 4 3 4 3 3 5% 7% 56%	2200
	21st to end	Night	15% 6% 2 6% 5% 4 3 3 5% 6% 45%	2200
October	1st to 10th	Night	11% 6% 2 6% 4 4 5% 3 5% 6% 50%	2233
	11th to 20th	Night	17% 9% 2 7% 4 3 3 3 5% 7% 40%	2400
	21st to end	Night	20% 7% 3 6% 4 4 4 3 5% 6% 38%	2771
November	1st to 10th	Night	13% 8% 2 6% 4 3 3 4 5% 6% 44%	2666
	11th to 20th	Night	16% 12% 4 7% 4 4 4 3 5% 7% 35%	2730
	21st to end	Night	20% 13% 4 9% 5% 4 5% 3 5% 6% 27%	2730
December	1st to 10th	Night	14% 11% 5% 11% 7% 6% 5% 4 6% 6% 25%	4380
	11th to 20th	Night	18% 18% 7% 12% 4 4 4 3 4 5% 22%	4952
	21st to end	Night	25% 20% 6% 10% 5% 4 4 3 4 5% 14%	7056

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	71% 5% 11% 9% 3	4692
	11th to 20th	Day	71% 4 6% 7% 11% 1	4968
	21st to end	Day	74% 3 7% 11% 5%	5780
February	1st to 10th	Day	65% 5% 10% 14% 6% 1	1890
	11th to 20th	Day	63% 5% 8% 16% 7% 1	2050
	21st to end	Day	57% 6% 13% 15% 7% 2	1730
March	1st to 10th	Day	61% 5% 8% 19% 7%	4707
	11th to 20th	Day	44% 6% 13% 26% 10% 1	5090
	21st to end	Day	59% 6% 11% 16% 7% 1	5586
April	1st to 10th	Day	54% 6% 11% 16% 12% 1	2431
	11th to 20th	Day	49% 6% 13% 19% 12% 2	2634
	21st to end	Day	49% 5% 12% 22% 10% 2	2730
May	1st to 10th	Day	55% 6% 11% 16% 12% 1	6027
	11th to 20th	Day	45% 7% 14% 21% 12% 1	5995
	21st to end	Day	42% 7% 11% 22% 15% 3	6590
June	1st to 10th	Day	41% 7% 11% 24% 14% 2	2669
	11th to 20th	Day	40% 7% 14% 22% 16% 2	2800
	21st to end	Day	38% 9% 16% 19% 15% 4	2800
July	1st to 10th	Day	38% 5% 11% 27% 17% 2	6291
	11th to 20th	Day	36% 7% 15% 25% 16% 1	6160
	21st to end	Day	38% 6% 13% 22% 19% 2	6240
August	1st to 10th	Day	36% 7% 15% 26% 15% 1	4221
	11th to 20th	Day	35% 7% 14% 31% 11% 1	4213
	21st to end	Day	34% 5% 13% 32% 12% 2	4548
September	1st to 10th	Day	35% 6% 13% 24% 18% 4	2250
	11th to 20th	Day	33% 6% 10% 28% 20% 3	2200
	21st to end	Day	43% 5% 10% 22% 20% 1	2200
October	1st to 10th	Day	27% 4 13% 34% 20% 1	3530
	11th to 20th	Day	37% 5% 11% 24% 21% 1	3240
	21st to end	Day	42% 4 10% 23% 19% 1	3315
November	1st to 10th	Day	40% 6% 11% 25% 17% 1	1852
	11th to 20th	Day	53% 4 10% 20% 11% 2	1890
	21st to end	Day	58% 5% 12% 17% 8%	1890
December	1st to 10th	Day	64% 4 14% 16% 3	3020
	11th to 20th	Day	65% 5% 10% 16% 4	3460
	21st to end	Day	77% 4 7% 8% 4	4137
January	1st to 10th	Night	69% 4 8% 15% 4	8233
	11th to 20th	Night	70% 4 8% 10% 8% 1	8003
	21st to end	Night	62% 4 13% 14% 7%	8401
February	1st to 10th	Night	62% 5% 11% 14% 6% 1	2730
	11th to 20th	Night	58% 5% 10% 18% 8% 1	2464
	21st to end	Night	59% 5% 11% 15% 9% 2	2076
March	1st to 10th	Night	52% 5% 10% 23% 9% 1	5365
	11th to 20th	Night	37% 6% 14% 28% 13% 1	5090
	21st to end	Night	48% 6% 10% 22% 13% 1	5588
April	1st to 10th	Night	50% 6% 11% 18% 14% 1	2206
	11th to 20th	Night	45% 7% 11% 18% 17% 2	1935
	21st to end	Night	47% 6% 10% 21% 14% 2	1890
May	1st to 10th	Night	57% 7% 8% 13% 13% 2	4150
	11th to 20th	Night	43% 7% 13% 22% 15% 1	4123
	21st to end	Night	38% 7% 13% 25% 15% 2	4528
June	1st to 10th	Night	35% 8% 12% 24% 18% 3	1727
	11th to 20th	Night	33% 9% 14% 25% 17% 3	1600
	21st to end	Night	34% 6% 16% 24% 16% 3	1600
July	1st to 10th	Night	35% 5% 12% 26% 18% 4	3580
	11th to 20th	Night	33% 6% 18% 26% 16% 1	3676
	21st to end	Night	36% 5% 13% 22% 21% 3	4297
August	1st to 10th	Night	38% 6% 14% 25% 15% 2	2904
	11th to 20th	Night	35% 6% 12% 30% 16% 1	2902
	21st to end	Night	32% 7% 14% 28% 17% 2	3345
September	1st to 10th	Night	32% 5% 12% 26% 19% 5%	2128
	11th to 20th	Night	28% 6% 11% 28% 26% 3	2200
	21st to end	Night	39% 6% 10% 23% 20% 3	2200
October	1st to 10th	Night	25% 4 8% 30% 31% 1	3649
	11th to 20th	Night	35% 4 10% 28% 22% 1	3899
	21st to end	Night	36% 3 9% 31% 18% 3	4471
November	1st to 10th	Night	40% 5% 11% 25% 18% 2	2666
	11th to 20th	Night	48% 5% 10% 22% 13% 2	2730
	21st to end	Night	58% 6% 11% 19% 7%	2730
December	1st to 10th	Night	58% 5% 11% 19% 7% 1	4380
	11th to 20th	Night	64% 4 14% 12% 5% 1	4954
	21st to end	Night	73% 5% 9% 9% 4	7056

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	24% 18% 33% 17% 7% 1	330
	11th to 20th	Day	26% 20% 37% 12% 4 1	330
	21st to end	Day	27% 18% 32% 19% 4 1	363
February	1st to 10th	Day	26% 16% 37% 15% 4 1	330
	11th to 20th	Day	25% 16% 34% 21% 3	330
	21st to end	Day	23% 20% 41% 14% 1	273
March	1st to 10th	Day	26% 17% 36% 16% 4 1	379
	11th to 20th	Day	24% 16% 32% 21% 6% 1	540
	21st to end	Day	28% 15% 32% 18% 6% 1	594
April	1st to 10th	Day	22% 15% 32% 20% 9% 1	540
	11th to 20th	Day	21% 18% 30% 18% 8% 4	532
	21st to end	Day	24% 13% 29% 24% 9% 2	540
May	1st to 10th	Day	25% 11% 32% 21% 9% 2	543
	11th to 20th	Day	20% 12% 25% 25% 14% 5%	567
	21st to end	Day	15% 7% 26% 24% 20% 8%	617
June	1st to 10th	Day	13% 8% 28% 29% 17% 6%	599
	11th to 20th	Day	12% 5% 28% 28% 22% 5%	730
	21st to end	Day	13% 6% 26% 28% 19% 7%	730
July	1st to 10th	Day	11% 3 20% 28% 23% 14%	721
	11th to 20th	Day	8% 4 24% 28% 24% 13%	671
	21st to end	Day	10% 4 17% 26% 29% 14%	576
August	1st to 10th	Day	9% 4 15% 25% 28% 18%	526
	11th to 20th	Day	10% 2 18% 31% 28% 12%	519
	21st to end	Day	8% 3 19% 26% 28% 16%	583
September	1st to 10th	Day	16% 4 18% 24% 25% 13%	530
	11th to 20th	Day	8% 3 14% 23% 33% 18%	530
	21st to end	Day	20% 9% 17% 24% 18% 10%	530
October	1st to 10th	Day	12% 8% 23% 27% 22% 8%	530
	11th to 20th	Day	16% 15% 29% 25% 12% 2	530
	21st to end	Day	22% 14% 39% 17% 6% 2	448
November	1st to 10th	Day	18% 14% 36% 19% 10% 3	330
	11th to 20th	Day	27% 18% 30% 18% 6%	330
	21st to end	Day	30% 16% 33% 18% 2	330
December	1st to 10th	Day	23% 20% 32% 18% 7% 1	330
	11th to 20th	Day	24% 18% 36% 18% 4	330
	21st to end	Day	28% 18% 34% 17% 3	363
January	1st to 10th	Night	25% 14% 35% 20% 5%	1050
	11th to 20th	Night	26% 17% 36% 17% 4 1	955
	21st to end	Night	24% 15% 36% 20% 4	924
February	1st to 10th	Night	27% 11% 34% 26% 3	840
	11th to 20th	Night	22% 13% 37% 24% 3	823
	21st to end	Night	27% 13% 38% 19% 2	692
March	1st to 10th	Night	23% 11% 35% 25% 6%	840
	11th to 20th	Night	19% 16% 35% 24% 6% 1	840
	21st to end	Night	23% 12% 32% 26% 7% 1	924
April	1st to 10th	Night	21% 15% 34% 24% 5% 1	736
	11th to 20th	Night	19% 12% 36% 24% 9% 1	623
	21st to end	Night	21% 8% 36% 27% 8%	630
May	1st to 10th	Night	22% 8% 27% 32% 9% 1	630
	11th to 20th	Night	22% 5% 29% 30% 14% 1	621
	21st to end	Night	14% 3 24% 39% 19% 3	683
June	1st to 10th	Night	12% 3 26% 41% 18% 1	600
	11th to 20th	Night	12% 2 22% 45% 18% 1	600
	21st to end	Night	11% 3 22% 38% 25% 1	600
July	1st to 10th	Night	11% 2 15% 42% 28% 3	585
	11th to 20th	Night	9% 3 16% 40% 28% 4	582
	21st to end	Night	10% 1 12% 44% 30% 3	657
August	1st to 10th	Night	9% 2 12% 43% 32% 3	597
	11th to 20th	Night	10% 2 12% 39% 32% 4	594
	21st to end	Night	8% 3 12% 39% 34% 4	660
September	1st to 10th	Night	13% 4 16% 34% 29% 5%	728
	11th to 20th	Night	11% 3 13% 36% 33% 5%	800
	21st to end	Night	17% 5% 21% 32% 23% 2	800
October	1st to 10th	Night	15% 5% 24% 32% 22% 3	800
	11th to 20th	Night	20% 12% 28% 28% 11% 1	800
	21st to end	Night	23% 12% 29% 28% 8%	880
November	1st to 10th	Night	17% 10% 33% 27% 12% 1	820
	11th to 20th	Night	22% 13% 32% 25% 8%	840
	21st to end	Night	28% 11% 31% 24% 5%	840
December	1st to 10th	Night	24% 14% 34% 23% 5%	840
	11th to 20th	Night	25% 14% 35% 22% 4	840
	21st to end	Night	33% 12% 31% 21% 3	1113

Page generated at 2026-05-29 01:53:25. Version ac07

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