Rembert
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rembert clear sky chart from 2005-11-06 to 2024-11-05.

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 5% 4 6% 8% 42%	101171
	Night	14% 6% 2 6% 4 4 4 4 6% 7% 43%	97826
Transparency	Day	37% 7% 12% 19% 18% 6%	104848
	Night	37% 7% 11% 18% 19% 7%	102275
Seeing	Day	14% 7% 22% 24% 21% 11%	15408
	Night	15% 6% 23% 33% 20% 3	25479

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% 6% 2 5% 3 3 3 3 5% 7% 47%	2836
	11th to 20th	Day	12% 5% 2 4 4 4 4 3 4 6% 53%	2840
	21st to end	Day	17% 9% 3 7% 4 4 4 2 3 4 43%	3124
February	1st to 10th	Day	15% 7% 3 7% 4 4 4 3 6% 7% 41%	1710
	11th to 20th	Day	19% 6% 2 7% 4 2 4 2 5% 5% 45%	1819
	21st to end	Day	17% 6% 2 6% 4 4 4 4 4 5% 42%	1660
March	1st to 10th	Day	22% 9% 3 7% 4 3 3 3 4 5% 36%	3435
	11th to 20th	Day	9% 4 2 5% 4 4 4 3 5% 7% 53%	3480
	21st to end	Day	18% 7% 3 5% 4 3 3 3 4 6% 43%	3815
April	1st to 10th	Day	9% 4 2 5% 4 4 4 4 6% 7% 50%	2095
	11th to 20th	Day	11% 5% 1 5% 4 4 5% 4 5% 8% 49%	2254
	21st to end	Day	9% 4 2 5% 4 4 4 4 6% 7% 52%	2344
May	1st to 10th	Day	9% 7% 3 6% 5% 4 5% 5% 7% 10% 40%	4082
	11th to 20th	Day	17% 7% 2 7% 4 4 4 4 5% 7% 38%	4081
	21st to end	Day	7% 3 1 5% 4 5% 5% 4 7% 10% 47%	4476
June	1st to 10th	Day	10% 5% 2 7% 6% 5% 6% 5% 8% 10% 36%	2470
	11th to 20th	Day	8% 5% 2 5% 5% 5% 6% 6% 8% 11% 41%	2470
	21st to end	Day	7% 4 2 6% 5% 5% 7% 6% 10% 11% 38%	2470
July	1st to 10th	Day	12% 6% 2 8% 6% 6% 6% 5% 8% 11% 29%	4120
	11th to 20th	Day	7% 5% 2 7% 6% 6% 6% 6% 10% 14% 31%	4120
	21st to end	Day	9% 8% 3 9% 6% 6% 6% 7% 10% 13% 25%	4466
August	1st to 10th	Day	24% 6% 2 7% 5% 5% 6% 5% 8% 11% 21%	4104
	11th to 20th	Day	11% 6% 2 6% 5% 5% 6% 5% 8% 11% 36%	4024
	21st to end	Day	7% 4 1 5% 4 4 6% 5% 8% 10% 46%	4180
September	1st to 10th	Day	8% 5% 2 6% 6% 6% 5% 4 6% 9% 43%	2139
	11th to 20th	Day	15% 6% 3 6% 5% 4 4 4 5% 8% 40%	2090
	21st to end	Day	18% 6% 2 6% 4 3 4 4 5% 7% 42%	2090
October	1st to 10th	Day	15% 5% 2 6% 3 3 4 3 4 6% 50%	1956
	11th to 20th	Day	10% 5% 2 4 3 3 3 3 3 6% 59%	1900
	21st to end	Day	11% 5% 2 4 3 3 3 3 4 5% 57%	2090
November	1st to 10th	Day	13% 5% 1 4 3 3 3 3 4 6% 54%	1898
	11th to 20th	Day	15% 6% 2 5% 3 2 3 3 4 5% 52%	1836
	21st to end	Day	14% 6% 2 5% 4 3 3 2 5% 7% 49%	1710
December	1st to 10th	Day	17% 8% 3 6% 5% 5% 3 3 5% 6% 39%	1710
	11th to 20th	Day	16% 4 1 4 3 3 3 3 4 6% 52%	2153
	21st to end	Day	19% 7% 3 5% 3 3 3 3 4 6% 44%	3124
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 4 6% 47%	4109
	11th to 20th	Night	11% 7% 2 7% 4 4 5% 4 5% 7% 44%	4120
	21st to end	Night	16% 8% 3 6% 4 4 3 3 4 5% 45%	4532
February	1st to 10th	Night	17% 6% 2 5% 4 4 4 4 5% 7% 43%	2470
	11th to 20th	Night	19% 7% 2 5% 5% 3 3 3 4 5% 44%	2243
	21st to end	Night	15% 6% 3 6% 4 5% 3 3 4 7% 45%	1791
March	1st to 10th	Night	23% 10% 3 7% 4 3 3 3 5% 6% 34%	3418
	11th to 20th	Night	11% 5% 2 5% 4 3 4 4 5% 7% 50%	3480
	21st to end	Night	18% 4 2 5% 4 4 4 3 6% 7% 44%	3817
April	1st to 10th	Night	11% 4 1 4 4 4 5% 4 7% 7% 50%	2084
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 52%	1875
	21st to end	Night	10% 4 1 6% 4 4 4 4 6% 6% 53%	1851
May	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 6% 9% 43%	2813
	11th to 20th	Night	14% 7% 2 7% 5% 4 4 4 6% 8% 39%	2812
	21st to end	Night	7% 4 2 5% 4 5% 5% 5% 7% 9% 47%	3079
June	1st to 10th	Night	12% 6% 2 7% 5% 6% 6% 4 8% 9% 35%	1710
	11th to 20th	Night	8% 6% 3 6% 6% 5% 6% 5% 8% 11% 38%	1710
	21st to end	Night	7% 5% 2 7% 5% 6% 6% 6% 10% 12% 35%	1710
July	1st to 10th	Night	13% 8% 3 7% 6% 5% 6% 6% 7% 10% 30%	2840
	11th to 20th	Night	9% 6% 3 7% 6% 6% 6% 6% 9% 12% 29%	2840
	21st to end	Night	13% 8% 4 9% 7% 7% 7% 5% 8% 9% 23%	3087
August	1st to 10th	Night	23% 6% 3 8% 5% 5% 6% 5% 8% 9% 22%	2825
	11th to 20th	Night	11% 6% 2 7% 6% 5% 6% 5% 8% 9% 36%	2785
	21st to end	Night	7% 4 1 4 3 4 4 4 8% 12% 49%	3462
September	1st to 10th	Night	8% 5% 2 6% 5% 6% 6% 5% 7% 10% 40%	2037
	11th to 20th	Night	14% 7% 3 7% 5% 5% 5% 3 5% 7% 40%	2090
	21st to end	Night	17% 6% 2 7% 4 4 4 3 5% 5% 43%	2090
October	1st to 10th	Night	14% 5% 3 5% 3 3 3 2 4 6% 52%	2223
	11th to 20th	Night	14% 4 1 4 4 3 3 3 4 5% 56%	2280
	21st to end	Night	9% 6% 2 4 3 3 3 3 5% 5% 57%	2508
November	1st to 10th	Night	12% 6% 2 4 3 3 3 2 4 5% 55%	2280
	11th to 20th	Night	14% 6% 2 4 3 3 3 3 4 5% 53%	2341
	21st to end	Night	14% 5% 2 5% 3 3 4 3 6% 6% 48%	2470
December	1st to 10th	Night	18% 7% 3 5% 4 3 4 3 5% 6% 43%	2470
	11th to 20th	Night	18% 5% 1 4 3 3 3 3 3 5% 52%	3042
	21st to end	Night	19% 7% 3 5% 3 3 4 3 5% 6% 41%	4532

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% 7% 24% 23% 7%	2837
	11th to 20th	Day	33% 4 6% 17% 30% 10%	2840
	21st to end	Day	45% 4 4 16% 23% 9%	3124
February	1st to 10th	Day	43% 4 9% 18% 20% 5%	1710
	11th to 20th	Day	43% 5% 5% 18% 24% 6%	1829
	21st to end	Day	43% 6% 8% 15% 20% 8%	1660
March	1st to 10th	Day	50% 5% 8% 14% 14% 10%	3435
	11th to 20th	Day	30% 6% 8% 16% 29% 11%	3480
	21st to end	Day	42% 5% 8% 18% 23% 5%	3815
April	1st to 10th	Day	31% 7% 10% 20% 26% 7%	2095
	11th to 20th	Day	32% 5% 11% 19% 21% 11%	2254
	21st to end	Day	30% 7% 11% 25% 23% 3	2344
May	1st to 10th	Day	36% 10% 16% 23% 13% 2	4120
	11th to 20th	Day	42% 8% 12% 21% 16% 1	4085
	21st to end	Day	27% 10% 18% 21% 22% 2	4489
June	1st to 10th	Day	39% 11% 17% 23% 10% 1	2470
	11th to 20th	Day	32% 10% 17% 25% 13% 1	2470
	21st to end	Day	34% 11% 18% 22% 13% 2	2470
July	1st to 10th	Day	44% 11% 19% 18% 7% 1	4055
	11th to 20th	Day	38% 14% 29% 14% 4 1	4051
	21st to end	Day	45% 14% 19% 17% 4 1	4324
August	1st to 10th	Day	54% 10% 20% 12% 4	4091
	11th to 20th	Day	38% 11% 18% 20% 13%	4063
	21st to end	Day	30% 8% 15% 32% 13% 2	4180
September	1st to 10th	Day	37% 10% 15% 16% 17% 4	2139
	11th to 20th	Day	40% 8% 11% 17% 21% 3	2090
	21st to end	Day	42% 6% 9% 21% 16% 6%	2090
October	1st to 10th	Day	34% 5% 6% 19% 28% 8%	3242
	11th to 20th	Day	17% 3 5% 18% 28% 28%	3140
	21st to end	Day	25% 3 5% 21% 30% 15%	3428
November	1st to 10th	Day	32% 4 8% 18% 27% 12%	1898
	11th to 20th	Day	35% 4 7% 19% 25% 10%	1836
	21st to end	Day	36% 4 9% 19% 22% 9%	1710
December	1st to 10th	Day	45% 5% 9% 18% 16% 6%	1710
	11th to 20th	Day	34% 3 7% 23% 23% 10%	2150
	21st to end	Day	42% 4 7% 21% 23% 3	3124
January	1st to 10th	Night	37% 6% 7% 19% 24% 8%	4109
	11th to 20th	Night	37% 6% 8% 19% 24% 6%	4120
	21st to end	Night	42% 6% 5% 14% 26% 8%	4532
February	1st to 10th	Night	40% 4 8% 18% 20% 9%	2470
	11th to 20th	Night	43% 4 7% 16% 21% 8%	2244
	21st to end	Night	39% 5% 9% 18% 18% 11%	1791
March	1st to 10th	Night	50% 7% 8% 13% 14% 7%	3418
	11th to 20th	Night	32% 6% 8% 13% 25% 16%	3480
	21st to end	Night	39% 6% 8% 21% 18% 8%	3817
April	1st to 10th	Night	32% 7% 11% 18% 23% 10%	2084
	11th to 20th	Night	32% 6% 9% 20% 22% 12%	1875
	21st to end	Night	30% 6% 12% 24% 23% 5%	1851
May	1st to 10th	Night	34% 11% 14% 25% 13% 3	2840
	11th to 20th	Night	40% 9% 14% 20% 17%	2813
	21st to end	Night	28% 12% 14% 25% 19% 3	3087
June	1st to 10th	Night	40% 11% 18% 20% 10% 2	1710
	11th to 20th	Night	36% 11% 17% 22% 11% 2	1710
	21st to end	Night	35% 14% 21% 20% 8% 2	1710
July	1st to 10th	Night	46% 12% 19% 16% 6% 2	2795
	11th to 20th	Night	42% 16% 24% 13% 4 1	2786
	21st to end	Night	53% 13% 15% 14% 4	2988
August	1st to 10th	Night	55% 10% 20% 13% 3 1	2814
	11th to 20th	Night	41% 12% 20% 20% 7%	2812
	21st to end	Night	26% 8% 16% 32% 15% 2	3462
September	1st to 10th	Night	38% 10% 14% 19% 13% 5%	2037
	11th to 20th	Night	43% 8% 11% 15% 18% 4	2090
	21st to end	Night	43% 7% 12% 18% 16% 4	2090
October	1st to 10th	Night	35% 4 8% 18% 28% 7%	3704
	11th to 20th	Night	21% 2 5% 15% 25% 32%	3779
	21st to end	Night	24% 4 6% 19% 27% 19%	4120
November	1st to 10th	Night	32% 4 8% 14% 27% 14%	2280
	11th to 20th	Night	34% 5% 6% 16% 25% 13%	2341
	21st to end	Night	35% 4 8% 19% 24% 10%	2470
December	1st to 10th	Night	42% 7% 10% 16% 19% 6%	2470
	11th to 20th	Night	36% 4 7% 19% 24% 10%	3044
	21st to end	Night	43% 5% 7% 19% 22% 4	4532

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% 15% 43% 20% 3	270
	11th to 20th	Day	16% 15% 40% 21% 7% 1	270
	21st to end	Day	21% 20% 37% 18% 4	297
February	1st to 10th	Day	17% 15% 39% 24% 6%	270
	11th to 20th	Day	29% 13% 39% 16% 2	270
	21st to end	Day	21% 17% 38% 18% 5% 1	315
March	1st to 10th	Day	18% 12% 32% 25% 12%	460
	11th to 20th	Day	17% 14% 41% 21% 7% 1	460
	21st to end	Day	17% 15% 36% 23% 9% 1	506
April	1st to 10th	Day	13% 15% 32% 23% 16% 1	460
	11th to 20th	Day	10% 10% 32% 23% 19% 6%	452
	21st to end	Day	12% 8% 24% 29% 19% 8%	460
May	1st to 10th	Day	10% 11% 29% 26% 18% 7%	463
	11th to 20th	Day	17% 4 16% 24% 25% 14%	487
	21st to end	Day	14% 5% 12% 24% 25% 21%	529
June	1st to 10th	Day	11% 2 11% 30% 30% 16%	490
	11th to 20th	Day	9% 3 14% 24% 29% 21%	490
	21st to end	Day	8% 2 10% 30% 31% 20%	490
July	1st to 10th	Day	8% 2 5% 22% 32% 31%	485
	11th to 20th	Day	10% 1 5% 20% 36% 29%	484
	21st to end	Day	7% 2 8% 24% 36% 22%	532
August	1st to 10th	Day	13% 1 9% 25% 30% 23%	486
	11th to 20th	Day	14% 3 6% 19% 34% 24%	479
	21st to end	Day	14% 2 7% 22% 33% 23%	539
September	1st to 10th	Day	10% 3 9% 27% 31% 19%	490
	11th to 20th	Day	18% 3 13% 19% 32% 14%	490
	21st to end	Day	18% 2 14% 25% 27% 13%	490
October	1st to 10th	Day	14% 5% 19% 30% 21% 11%	490
	11th to 20th	Day	8% 7% 23% 30% 23% 9%	490
	21st to end	Day	11% 6% 25% 29% 22% 8%	539
November	1st to 10th	Day	15% 6% 26% 28% 18% 7%	472
	11th to 20th	Day	19% 8% 33% 28% 11% 2	396
	21st to end	Day	11% 10% 31% 29% 16% 2	270
December	1st to 10th	Day	22% 12% 35% 22% 9%	270
	11th to 20th	Day	20% 10% 32% 24% 11% 2	270
	21st to end	Day	25% 12% 31% 20% 9% 2	297
January	1st to 10th	Night	21% 10% 33% 27% 8%	760
	11th to 20th	Night	18% 11% 31% 33% 7%	760
	21st to end	Night	19% 9% 37% 32% 3	836
February	1st to 10th	Night	19% 11% 33% 32% 6%	760
	11th to 20th	Night	22% 10% 36% 30% 2	743
	21st to end	Night	16% 13% 37% 28% 6%	628
March	1st to 10th	Night	18% 10% 32% 34% 6%	760
	11th to 20th	Night	16% 11% 36% 29% 8%	760
	21st to end	Night	15% 10% 36% 30% 9%	836
April	1st to 10th	Night	14% 14% 33% 31% 8%	760
	11th to 20th	Night	13% 9% 28% 34% 15% 1	751
	21st to end	Night	11% 7% 28% 42% 12%	711
May	1st to 10th	Night	11% 6% 27% 41% 15%	570
	11th to 20th	Night	13% 4 23% 38% 20% 2	561
	21st to end	Night	10% 3 10% 39% 34% 5%	617
June	1st to 10th	Night	14% 2 12% 39% 28% 4	570
	11th to 20th	Night	9% 3 13% 33% 33% 9%	570
	21st to end	Night	8% 2 9% 41% 33% 7%	570
July	1st to 10th	Night	11% 1 8% 32% 39% 8%	555
	11th to 20th	Night	9% 1 5% 29% 48% 8%	552
	21st to end	Night	7% 2 6% 35% 43% 7%	624
August	1st to 10th	Night	14% 2 7% 26% 44% 8%	567
	11th to 20th	Night	12% 2 5% 33% 42% 6%	564
	21st to end	Night	13% 3 8% 27% 43% 7%	822
September	1st to 10th	Night	10% 3 8% 30% 43% 5%	760
	11th to 20th	Night	15% 3 11% 30% 35% 6%	760
	21st to end	Night	20% 3 13% 33% 28% 3	760
October	1st to 10th	Night	16% 3 15% 33% 29% 4	760
	11th to 20th	Night	14% 4 23% 33% 24% 3	760
	21st to end	Night	11% 6% 23% 34% 24% 3	836
November	1st to 10th	Night	15% 6% 22% 35% 19% 4	760
	11th to 20th	Night	17% 9% 28% 33% 12% 1	760
	21st to end	Night	15% 7% 27% 33% 16% 1	760
December	1st to 10th	Night	20% 7% 27% 36% 10% 1	760
	11th to 20th	Night	19% 5% 28% 35% 12% 1	760
	21st to end	Night	22% 11% 24% 33% 9%	836

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