Conway
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Conway clear sky chart from 2005-11-06 to 2024-10-25.

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	16% 7% 2 6% 5% 4 5% 4 6% 7% 37%	101248
	Night	17% 8% 2 6% 4 4 5% 4 6% 7% 38%	97574
Transparency	Day	45% 7% 13% 21% 13% 2	101006
	Night	45% 7% 13% 21% 12% 2	97436
Seeing	Day	22% 15% 29% 22% 9% 3	14861
	Night	20% 10% 28% 31% 10% 1	23686

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	14% 9% 2 6% 6% 5% 5% 4 5% 6% 38%	2517
	11th to 20th	Day	14% 8% 3 7% 5% 6% 6% 5% 5% 6% 35%	2520
	21st to end	Day	14% 11% 3 7% 5% 4 4 3 6% 7% 36%	2772
February	1st to 10th	Day	13% 10% 3 7% 5% 5% 5% 4 5% 7% 37%	1670
	11th to 20th	Day	12% 7% 3 8% 5% 5% 4 5% 7% 7% 38%	1848
	21st to end	Day	14% 11% 3 6% 5% 6% 6% 4 5% 5% 35%	1570
March	1st to 10th	Day	20% 15% 3 7% 5% 4 4 4 4 5% 29%	3116
	11th to 20th	Day	14% 8% 3 6% 4 5% 5% 4 6% 6% 39%	3342
	21st to end	Day	21% 8% 3 7% 5% 3 3 3 4 7% 36%	4024
April	1st to 10th	Day	18% 10% 3 6% 5% 3 4 3 4 6% 37%	2280
	11th to 20th	Day	16% 7% 2 5% 6% 4 5% 4 5% 8% 38%	2304
	21st to end	Day	21% 9% 3 7% 5% 4 4 3 5% 5% 35%	2470
May	1st to 10th	Day	21% 12% 4 8% 5% 5% 5% 3 5% 6% 26%	4106
	11th to 20th	Day	18% 8% 2 8% 6% 5% 5% 4 5% 6% 32%	4261
	21st to end	Day	14% 5% 2 6% 4 5% 6% 5% 7% 9% 38%	4837
June	1st to 10th	Day	21% 7% 2 6% 5% 5% 5% 4 6% 7% 31%	2660
	11th to 20th	Day	16% 7% 2 6% 5% 4 4 4 7% 7% 38%	2660
	21st to end	Day	20% 7% 2 6% 5% 5% 5% 5% 6% 8% 31%	2660
July	1st to 10th	Day	13% 5% 3 6% 5% 4 5% 5% 7% 10% 37%	4440
	11th to 20th	Day	11% 5% 2 6% 4 5% 6% 5% 7% 11% 39%	4440
	21st to end	Day	18% 6% 2 7% 4 4 5% 4 6% 7% 37%	4814
August	1st to 10th	Day	14% 6% 2 7% 5% 6% 6% 4 6% 8% 36%	4233
	11th to 20th	Day	18% 8% 3 8% 5% 5% 5% 4 6% 7% 33%	4045
	21st to end	Day	10% 4 2 5% 4 4 5% 4 6% 9% 46%	4225
September	1st to 10th	Day	12% 4 1 4 3 4 4 4 7% 9% 48%	2276
	11th to 20th	Day	13% 4 2 3 3 3 4 3 4 5% 54%	2090
	21st to end	Day	16% 4 2 5% 4 4 5% 3 5% 6% 46%	2090
October	1st to 10th	Day	20% 6% 2 6% 4 4 4 3 4 6% 40%	2090
	11th to 20th	Day	16% 7% 2 5% 4 4 4 3 5% 7% 43%	1812
	21st to end	Day	23% 8% 2 5% 4 4 4 4 5% 5% 35%	1825
November	1st to 10th	Day	14% 6% 2 5% 4 5% 4 4 5% 7% 45%	1671
	11th to 20th	Day	18% 5% 1 4 4 5% 4 4 7% 8% 40%	1710
	21st to end	Day	19% 7% 3 4 3 4 4 4 5% 6% 40%	1672
December	1st to 10th	Day	19% 9% 3 7% 5% 5% 5% 4 5% 6% 32%	1520
	11th to 20th	Day	20% 9% 3 5% 4 4 4 3 4 5% 40%	1906
	21st to end	Day	22% 11% 3 6% 4 4 4 4 6% 5% 30%	2772
January	1st to 10th	Night	15% 8% 3 6% 4 4 4 4 5% 7% 41%	4429
	11th to 20th	Night	11% 9% 3 10% 7% 6% 6% 5% 7% 7% 30%	4440
	21st to end	Night	16% 10% 4 11% 5% 5% 5% 3 5% 6% 29%	4884
February	1st to 10th	Night	12% 9% 3 7% 5% 5% 5% 4 6% 7% 36%	2504
	11th to 20th	Night	10% 9% 3 6% 5% 5% 6% 4 6% 6% 42%	2218
	21st to end	Night	12% 10% 3 5% 4 4 4 4 6% 8% 39%	1884
March	1st to 10th	Night	24% 10% 3 5% 4 4 4 4 4 5% 32%	3724
	11th to 20th	Night	12% 10% 3 8% 6% 6% 6% 4 6% 6% 32%	3615
	21st to end	Night	21% 10% 3 7% 4 3 4 3 5% 6% 34%	3606
April	1st to 10th	Night	17% 10% 2 7% 4 4 4 3 4 6% 38%	1900
	11th to 20th	Night	17% 7% 2 6% 6% 4 4 4 6% 7% 38%	1825
	21st to end	Night	23% 6% 2 4 4 4 4 3 6% 6% 38%	1710
May	1st to 10th	Night	23% 12% 3 7% 4 5% 5% 3 5% 6% 27%	2834
	11th to 20th	Night	18% 9% 4 8% 5% 6% 5% 5% 6% 7% 28%	2660
	21st to end	Night	15% 6% 2 6% 4 4 4 4 6% 8% 41%	2738
June	1st to 10th	Night	21% 7% 2 5% 4 4 4 4 6% 7% 36%	1520
	11th to 20th	Night	19% 6% 2 3 4 4 5% 4 6% 7% 41%	1520
	21st to end	Night	19% 6% 2 5% 5% 4 4 4 6% 8% 37%	1520
July	1st to 10th	Night	13% 5% 1 5% 4 4 5% 5% 8% 9% 40%	2520
	11th to 20th	Night	15% 5% 1 6% 4 4 5% 3 5% 7% 45%	2520
	21st to end	Night	16% 5% 2 5% 5% 4 4 4 7% 7% 41%	2739
August	1st to 10th	Night	21% 7% 3 7% 5% 4 5% 4 6% 5% 34%	2664
	11th to 20th	Night	16% 7% 2 8% 5% 4 4 4 5% 7% 37%	2782
	21st to end	Night	10% 5% 2 4 4 3 4 4 6% 8% 49%	3429
September	1st to 10th	Night	12% 4 2 5% 3 3 3 4 5% 7% 53%	1903
	11th to 20th	Night	15% 5% 1 4 3 3 4 3 4 6% 53%	2090
	21st to end	Night	16% 5% 2 5% 3 3 3 3 5% 7% 47%	2090
October	1st to 10th	Night	19% 6% 2 6% 4 4 4 3 6% 6% 39%	2090
	11th to 20th	Night	16% 6% 2 5% 4 4 4 4 6% 7% 41%	2362
	21st to end	Night	24% 7% 2 5% 5% 4 4 3 5% 5% 37%	2637
November	1st to 10th	Night	15% 5% 2 6% 4 4 5% 3 6% 6% 44%	2407
	11th to 20th	Night	16% 6% 2 6% 5% 4 5% 3 5% 6% 42%	2470
	21st to end	Night	15% 8% 2 6% 4 4 5% 4 4 7% 43%	2508
December	1st to 10th	Night	18% 10% 2 6% 6% 5% 4 4 4 5% 36%	2660
	11th to 20th	Night	19% 9% 2 5% 4 4 4 4 5% 5% 38%	3288
	21st to end	Night	20% 10% 3 7% 5% 4 4 3 5% 6% 34%	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	42% 6% 13% 27% 11% 1	2518
	11th to 20th	Day	46% 8% 13% 22% 9% 2	2520
	21st to end	Day	47% 7% 13% 21% 11% 1	2772
February	1st to 10th	Day	47% 6% 15% 19% 11% 2	1670
	11th to 20th	Day	45% 7% 11% 19% 14% 4	1857
	21st to end	Day	50% 6% 12% 17% 13% 3	1570
March	1st to 10th	Day	59% 6% 8% 12% 13% 3	3119
	11th to 20th	Day	42% 8% 14% 16% 14% 6%	3342
	21st to end	Day	49% 4 7% 15% 20% 5%	4024
April	1st to 10th	Day	48% 6% 10% 20% 14% 4	2280
	11th to 20th	Day	44% 7% 12% 20% 15% 2	2304
	21st to end	Day	51% 6% 9% 17% 13% 3	2470
May	1st to 10th	Day	57% 8% 10% 16% 8% 1	4120
	11th to 20th	Day	51% 9% 14% 15% 9% 2	4265
	21st to end	Day	38% 8% 15% 22% 14% 1	4837
June	1st to 10th	Day	51% 7% 13% 20% 9% 1	2660
	11th to 20th	Day	43% 6% 14% 19% 15% 3	2660
	21st to end	Day	50% 9% 12% 18% 10% 1	2660
July	1st to 10th	Day	40% 7% 14% 24% 14%	4370
	11th to 20th	Day	37% 8% 17% 27% 10%	4365
	21st to end	Day	44% 7% 12% 22% 15% 1	4661
August	1st to 10th	Day	45% 7% 15% 23% 9%	4219
	11th to 20th	Day	49% 7% 14% 23% 7%	4084
	21st to end	Day	32% 8% 16% 26% 17% 2	4225
September	1st to 10th	Day	32% 8% 14% 29% 16% 1	2276
	11th to 20th	Day	32% 4 9% 33% 19% 2	2090
	21st to end	Day	38% 6% 12% 24% 19% 1	2090
October	1st to 10th	Day	46% 7% 11% 20% 15% 2	2090
	11th to 20th	Day	40% 6% 14% 29% 10% 2	1812
	21st to end	Day	50% 6% 11% 19% 12% 3	1825
November	1st to 10th	Day	37% 7% 15% 25% 14% 2	1671
	11th to 20th	Day	41% 6% 14% 19% 17% 3	1710
	21st to end	Day	44% 6% 17% 20% 12% 1	1672
December	1st to 10th	Day	52% 6% 13% 20% 9% 1	1520
	11th to 20th	Day	47% 5% 10% 18% 17% 2	1906
	21st to end	Day	54% 7% 10% 18% 9% 2	2772
January	1st to 10th	Night	41% 7% 14% 25% 10% 3	4429
	11th to 20th	Night	46% 9% 15% 17% 10% 2	4440
	21st to end	Night	53% 8% 11% 17% 10% 2	4884
February	1st to 10th	Night	47% 6% 13% 18% 14% 3	2504
	11th to 20th	Night	41% 7% 12% 22% 15% 3	2220
	21st to end	Night	44% 7% 12% 20% 13% 4	1884
March	1st to 10th	Night	54% 5% 11% 17% 11% 2	3734
	11th to 20th	Night	47% 10% 12% 16% 12% 3	3616
	21st to end	Night	51% 5% 7% 14% 19% 5%	3606
April	1st to 10th	Night	48% 5% 10% 19% 15% 3	1900
	11th to 20th	Night	45% 6% 10% 22% 15% 1	1825
	21st to end	Night	47% 5% 12% 18% 15% 3	1710
May	1st to 10th	Night	57% 9% 10% 17% 7% 1	2840
	11th to 20th	Night	52% 10% 13% 16% 8% 2	2661
	21st to end	Night	38% 9% 18% 20% 13% 2	2739
June	1st to 10th	Night	48% 8% 13% 19% 13%	1520
	11th to 20th	Night	43% 9% 15% 19% 13% 2	1520
	21st to end	Night	45% 9% 14% 21% 10% 1	1520
July	1st to 10th	Night	37% 9% 19% 21% 14%	2480
	11th to 20th	Night	39% 7% 15% 25% 14%	2472
	21st to end	Night	40% 7% 13% 28% 11% 1	2651
August	1st to 10th	Night	50% 7% 14% 20% 8%	2654
	11th to 20th	Night	45% 8% 16% 20% 11%	2809
	21st to end	Night	31% 7% 18% 28% 15% 1	3429
September	1st to 10th	Night	31% 7% 14% 31% 16%	1903
	11th to 20th	Night	33% 6% 11% 29% 19% 2	2090
	21st to end	Night	37% 7% 13% 28% 14% 2	2090
October	1st to 10th	Night	45% 7% 13% 21% 13% 2	2090
	11th to 20th	Night	40% 7% 14% 26% 11% 1	2362
	21st to end	Night	50% 5% 11% 20% 12% 2	2637
November	1st to 10th	Night	40% 6% 12% 24% 15% 2	2407
	11th to 20th	Night	42% 6% 11% 23% 15% 2	2470
	21st to end	Night	42% 6% 16% 23% 12% 1	2508
December	1st to 10th	Night	50% 7% 12% 21% 9% 1	2660
	11th to 20th	Night	46% 7% 12% 17% 17% 1	3288
	21st to end	Night	53% 7% 10% 20% 10% 1	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	26% 18% 27% 22% 7% 1	180
	11th to 20th	Day	26% 22% 23% 23% 5% 1	180
	21st to end	Day	17% 19% 34% 22% 8%	198
February	1st to 10th	Day	23% 23% 32% 18% 4	300
	11th to 20th	Day	23% 22% 35% 17% 3	456
	21st to end	Day	24% 20% 28% 23% 4	382
March	1st to 10th	Day	26% 18% 30% 22% 4	460
	11th to 20th	Day	26% 22% 30% 16% 6% 1	460
	21st to end	Day	26% 19% 30% 16% 7% 3	506
April	1st to 10th	Day	31% 18% 27% 15% 7% 2	460
	11th to 20th	Day	26% 22% 27% 15% 7% 2	452
	21st to end	Day	28% 21% 30% 13% 6% 2	460
May	1st to 10th	Day	32% 17% 29% 16% 4 2	463
	11th to 20th	Day	22% 17% 33% 19% 7% 2	487
	21st to end	Day	21% 16% 32% 21% 9% 2	529
June	1st to 10th	Day	21% 15% 35% 19% 9% 2	490
	11th to 20th	Day	17% 17% 31% 23% 8% 3	490
	21st to end	Day	22% 13% 36% 16% 12% 2	490
July	1st to 10th	Day	18% 9% 31% 24% 14% 3	485
	11th to 20th	Day	13% 7% 36% 30% 13% 3	484
	21st to end	Day	15% 9% 32% 28% 13% 3	532
August	1st to 10th	Day	11% 12% 27% 28% 17% 5%	486
	11th to 20th	Day	16% 10% 28% 26% 14% 7%	479
	21st to end	Day	12% 9% 26% 31% 15% 6%	539
September	1st to 10th	Day	16% 9% 24% 27% 18% 6%	490
	11th to 20th	Day	18% 10% 24% 21% 15% 11%	490
	21st to end	Day	17% 11% 27% 25% 13% 6%	490
October	1st to 10th	Day	25% 13% 21% 22% 14% 6%	490
	11th to 20th	Day	21% 14% 24% 25% 14% 3	417
	21st to end	Day	32% 10% 26% 24% 7% 1	411
November	1st to 10th	Day	20% 16% 26% 28% 8% 2	365
	11th to 20th	Day	28% 16% 26% 22% 8% 1	370
	21st to end	Day	27% 16% 30% 20% 7%	332
December	1st to 10th	Day	23% 27% 21% 21% 7% 1	180
	11th to 20th	Day	27% 21% 32% 15% 4	180
	21st to end	Day	31% 17% 29% 19% 4 1	198
January	1st to 10th	Night	18% 12% 35% 31% 4	760
	11th to 20th	Night	23% 15% 29% 29% 4	760
	21st to end	Night	17% 14% 36% 27% 6% 1	836
February	1st to 10th	Night	19% 14% 34% 30% 3	760
	11th to 20th	Night	17% 14% 42% 23% 4	743
	21st to end	Night	19% 14% 34% 29% 4	628
March	1st to 10th	Night	22% 14% 32% 28% 3	760
	11th to 20th	Night	21% 15% 31% 27% 6%	760
	21st to end	Night	23% 12% 30% 25% 9% 1	836
April	1st to 10th	Night	24% 13% 30% 28% 5%	760
	11th to 20th	Night	21% 14% 32% 28% 6%	701
	21st to end	Night	26% 14% 26% 27% 6%	570
May	1st to 10th	Night	25% 10% 26% 29% 7% 1	570
	11th to 20th	Night	20% 10% 30% 30% 11%	474
	21st to end	Night	18% 7% 23% 39% 12% 1	411
June	1st to 10th	Night	21% 7% 26% 34% 11% 1	380
	11th to 20th	Night	21% 6% 22% 36% 15%	380
	21st to end	Night	20% 3 23% 40% 13% 1	380
July	1st to 10th	Night	17% 2 19% 43% 19% 1	370
	11th to 20th	Night	15% 2 19% 42% 21% 2	368
	21st to end	Night	14% 3 16% 48% 19% 1	416
August	1st to 10th	Night	17% 3 17% 42% 20% 1	471
	11th to 20th	Night	16% 5% 23% 37% 18% 2	562
	21st to end	Night	16% 3 18% 38% 21% 4	802
September	1st to 10th	Night	14% 4 22% 38% 20% 2	760
	11th to 20th	Night	17% 5% 21% 30% 22% 6%	760
	21st to end	Night	18% 6% 23% 31% 18% 3	760
October	1st to 10th	Night	23% 8% 21% 31% 17% 1	760
	11th to 20th	Night	20% 9% 29% 29% 13% 1	760
	21st to end	Night	29% 9% 26% 29% 7%	812
November	1st to 10th	Night	19% 11% 29% 31% 9% 1	740
	11th to 20th	Night	21% 14% 28% 27% 8% 1	760
	21st to end	Night	21% 16% 27% 29% 6% 1	760
December	1st to 10th	Night	24% 11% 36% 23% 5% 1	760
	11th to 20th	Night	23% 15% 28% 30% 3	760
	21st to end	Night	23% 13% 32% 29% 3	836

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