Hannibal
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hannibal clear sky chart from 2005-11-06 to 2025-03-12.

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% 8% 3 7% 4 4 4 4 6% 7% 41%	108977
	Night	13% 9% 3 7% 4 4 4 3 5% 6% 42%	110246
Transparency	Day	25% 42% 7% 15% 10% 1	112611
	Night	27% 41% 6% 15% 11% 1	114752
Seeing	Day	14% 10% 28% 27% 16% 5%	16094
	Night	16% 9% 30% 30% 13% 1	26115

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	13% 12% 6% 13% 7% 5% 4 4 5% 5% 27%	3617
	11th to 20th	Day	9% 9% 4 9% 6% 6% 6% 4 5% 6% 35%	3959
	21st to end	Day	16% 15% 7% 9% 5% 3 3 3 3 4 31%	4488
February	1st to 10th	Day	15% 11% 5% 9% 5% 5% 5% 3 5% 7% 31%	1800
	11th to 20th	Day	13% 11% 3 8% 5% 5% 6% 4 5% 6% 35%	1847
	21st to end	Day	14% 10% 4 7% 4 4 4 3 4 6% 40%	1650
March	1st to 10th	Day	17% 11% 3 6% 3 3 3 3 4 4 42%	3373
	11th to 20th	Day	10% 7% 2 5% 4 3 5% 3 5% 7% 48%	3491
	21st to end	Day	17% 12% 4 8% 5% 4 4 3 5% 6% 32%	3959
April	1st to 10th	Day	14% 8% 3 8% 4 4 4 4 6% 7% 39%	2280
	11th to 20th	Day	16% 7% 2 8% 5% 4 3 3 5% 7% 40%	2254
	21st to end	Day	19% 6% 3 7% 5% 4 4 3 6% 7% 36%	2280
May	1st to 10th	Day	11% 8% 3 7% 5% 5% 5% 4 7% 10% 34%	3974
	11th to 20th	Day	16% 8% 3 7% 4 4 4 3 5% 8% 38%	4399
	21st to end	Day	10% 6% 2 6% 4 4 4 4 5% 7% 46%	4824
June	1st to 10th	Day	5% 4 2 6% 4 5% 5% 5% 7% 10% 46%	2660
	11th to 20th	Day	7% 5% 2 6% 4 4 5% 5% 7% 9% 47%	2660
	21st to end	Day	8% 5% 2 7% 5% 5% 5% 4 6% 10% 44%	2660
July	1st to 10th	Day	11% 6% 2 7% 4 4 5% 5% 7% 10% 38%	4440
	11th to 20th	Day	4 4 2 6% 4 4 5% 4 7% 10% 49%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 9% 11% 39%	4537
August	1st to 10th	Day	4 4 2 5% 4 4 5% 5% 8% 11% 48%	4104
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 9% 42%	3850
	21st to end	Day	5% 4 2 5% 3 4 5% 4 7% 10% 51%	4180
September	1st to 10th	Day	10% 6% 2 4 3 4 4 3 5% 7% 52%	2280
	11th to 20th	Day	10% 4 2 5% 4 4 3 4 6% 8% 52%	2280
	21st to end	Day	8% 5% 1 5% 4 5% 4 4 6% 8% 51%	2024
October	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 5% 6% 53%	1900
	11th to 20th	Day	14% 7% 3 5% 3 3 3 3 4 5% 48%	1900
	21st to end	Day	17% 8% 3 6% 4 3 3 3 4 6% 44%	2090
November	1st to 10th	Day	11% 7% 3 5% 3 3 3 3 5% 6% 51%	1772
	11th to 20th	Day	15% 7% 3 7% 4 3 3 3 5% 7% 44%	1800
	21st to end	Day	17% 11% 3 7% 4 4 3 4 4 5% 38%	1605
December	1st to 10th	Day	7% 9% 3 6% 5% 3 3 3 4 6% 51%	2610
	11th to 20th	Day	13% 9% 6% 10% 4 5% 4 3 5% 7% 34%	3008
	21st to end	Day	20% 20% 6% 11% 5% 4 4 3 3 5% 19%	3982
January	1st to 10th	Night	14% 11% 6% 13% 5% 5% 4 3 4 5% 29%	6348
	11th to 20th	Night	12% 13% 5% 11% 5% 5% 6% 4 5% 4 30%	6020
	21st to end	Night	16% 14% 5% 9% 5% 3 3 3 4 6% 31%	6490
February	1st to 10th	Night	15% 13% 5% 7% 5% 5% 4 4 5% 6% 33%	2600
	11th to 20th	Night	14% 9% 3 7% 5% 5% 4 3 4 7% 38%	2439
	21st to end	Night	15% 8% 3 7% 3 4 3 3 4 6% 43%	1980
March	1st to 10th	Night	18% 11% 3 5% 3 3 3 3 4 4 41%	3731
	11th to 20th	Night	13% 7% 2 6% 4 3 3 3 3 6% 50%	3497
	21st to end	Night	20% 10% 4 8% 6% 4 5% 4 5% 6% 29%	3672
April	1st to 10th	Night	12% 7% 3 7% 5% 4 4 3 5% 7% 45%	1900
	11th to 20th	Night	14% 7% 2 6% 4 5% 3 4 5% 6% 45%	1875
	21st to end	Night	17% 8% 3 7% 4 3 4 3 4 5% 41%	1900
May	1st to 10th	Night	16% 8% 3 7% 5% 4 5% 4 6% 7% 36%	2922
	11th to 20th	Night	12% 7% 3 7% 5% 4 4 4 5% 8% 41%	2506
	21st to end	Night	7% 6% 2 6% 4 4 4 4 6% 9% 49%	2743
June	1st to 10th	Night	7% 5% 2 5% 3 4 4 4 6% 9% 53%	1520
	11th to 20th	Night	7% 5% 2 6% 4 4 4 4 7% 8% 49%	1520
	21st to end	Night	6% 4 2 4 4 5% 5% 5% 5% 10% 50%	1520
July	1st to 10th	Night	11% 7% 2 7% 4 4 4 4 6% 9% 42%	2530
	11th to 20th	Night	4 3 2 4 4 4 4 3 6% 8% 58%	2530
	21st to end	Night	7% 5% 2 6% 5% 4 5% 5% 8% 10% 43%	3022
August	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 10% 59%	2836
	11th to 20th	Night	9% 5% 2 6% 4 4 4 3 5% 7% 52%	2980
	21st to end	Night	4 3 1 5% 3 4 5% 4 7% 11% 54%	3476
September	1st to 10th	Night	10% 5% 1 4 2 4 3 4 5% 6% 56%	1900
	11th to 20th	Night	7% 6% 2 6% 4 4 4 4 5% 7% 52%	1900
	21st to end	Night	7% 4 2 5% 4 4 4 3 4 7% 54%	2133
October	1st to 10th	Night	9% 4 2 4 3 3 3 4 5% 7% 57%	2280
	11th to 20th	Night	14% 5% 1 5% 3 3 3 3 3 5% 53%	2280
	21st to end	Night	17% 8% 2 5% 4 4 3 3 6% 5% 44%	2508
November	1st to 10th	Night	10% 6% 2 6% 3 3 3 3 4 6% 54%	2523
	11th to 20th	Night	12% 8% 3 6% 5% 4 3 3 5% 6% 46%	2600
	21st to end	Night	17% 10% 3 6% 3 3 3 3 5% 6% 41%	2790
December	1st to 10th	Night	10% 8% 3 7% 5% 3 4 3 5% 6% 47%	4580
	11th to 20th	Night	15% 9% 3 7% 4 4 4 4 5% 6% 40%	5199
	21st to end	Night	23% 17% 6% 10% 5% 4 4 3 4 4 20%	6996

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	48% 25% 6% 14% 6% 1	3618
	11th to 20th	Day	37% 25% 9% 12% 11% 6%	3959
	21st to end	Day	44% 27% 5% 13% 10% 2	4488
February	1st to 10th	Day	21% 61% 5% 8% 5% 1	1800
	11th to 20th	Day	22% 61% 3 8% 6% 1	1856
	21st to end	Day	17% 61% 3 9% 8% 1	1650
March	1st to 10th	Day	30% 38% 4 13% 13% 1	3373
	11th to 20th	Day	18% 39% 7% 19% 15% 2	3491
	21st to end	Day	33% 39% 12% 13% 3	3959
April	1st to 10th	Day	20% 64% 4 8% 4	2280
	11th to 20th	Day	16% 65% 3 9% 6%	2254
	21st to end	Day	17% 65% 3 8% 7% 1	2280
May	1st to 10th	Day	27% 39% 9% 17% 8%	4009
	11th to 20th	Day	29% 39% 7% 20% 5%	4403
	21st to end	Day	21% 39% 4 18% 18%	4837
June	1st to 10th	Day	10% 65% 6% 11% 6% 2	2660
	11th to 20th	Day	13% 66% 3 10% 6% 1	2660
	21st to end	Day	14% 64% 7% 9% 5% 1	2660
July	1st to 10th	Day	29% 36% 7% 18% 8% 1	4371
	11th to 20th	Day	20% 36% 9% 22% 12%	4365
	21st to end	Day	24% 36% 16% 17% 7%	4394
August	1st to 10th	Day	18% 37% 10% 27% 7%	4090
	11th to 20th	Day	27% 37% 8% 18% 10%	3889
	21st to end	Day	20% 38% 13% 22% 6% 2	4179
September	1st to 10th	Day	11% 60% 5% 12% 9% 3	2280
	11th to 20th	Day	12% 59% 5% 13% 9% 3	2280
	21st to end	Day	14% 60% 4 12% 9% 1	2024
October	1st to 10th	Day	13% 36% 2 7% 38% 4	3160
	11th to 20th	Day	10% 36% 3 14% 29% 7%	3140
	21st to end	Day	26% 36% 4 15% 19% 1	3428
November	1st to 10th	Day	17% 55% 5% 11% 9% 2	1772
	11th to 20th	Day	18% 57% 3 10% 11% 2	1800
	21st to end	Day	24% 56% 4 12% 4	1605
December	1st to 10th	Day	20% 34% 11% 23% 11%	2610
	11th to 20th	Day	36% 30% 8% 16% 9% 1	3005
	21st to end	Day	58% 25% 8% 7% 2	3982
January	1st to 10th	Night	48% 25% 8% 16% 4	6348
	11th to 20th	Night	45% 25% 6% 12% 10% 2	6020
	21st to end	Night	43% 27% 5% 15% 10% 1	6490
February	1st to 10th	Night	20% 61% 5% 7% 5% 1	2600
	11th to 20th	Night	19% 60% 4 9% 6%	2440
	21st to end	Night	16% 61% 3 8% 10% 2	1980
March	1st to 10th	Night	32% 38% 4 14% 11% 1	3731
	11th to 20th	Night	19% 39% 4 18% 16% 4	3497
	21st to end	Night	34% 39% 6% 18% 3	3672
April	1st to 10th	Night	17% 65% 5% 8% 4 1	1900
	11th to 20th	Night	13% 66% 4 10% 7% 1	1875
	21st to end	Night	17% 65% 2 7% 7% 1	1900
May	1st to 10th	Night	31% 39% 8% 14% 7%	2952
	11th to 20th	Night	27% 39% 9% 20% 4	2507
	21st to end	Night	20% 38% 7% 14% 19% 1	2751
June	1st to 10th	Night	9% 65% 6% 10% 8% 2	1520
	11th to 20th	Night	13% 65% 3 10% 8% 1	1520
	21st to end	Night	10% 65% 7% 13% 6% 1	1520
July	1st to 10th	Night	29% 36% 8% 18% 7% 2	2490
	11th to 20th	Night	15% 35% 8% 24% 17% 1	2482
	21st to end	Night	25% 35% 14% 16% 10%	2926
August	1st to 10th	Night	13% 37% 13% 25% 12%	2826
	11th to 20th	Night	23% 37% 7% 18% 15%	3007
	21st to end	Night	18% 37% 15% 22% 7% 1	3476
September	1st to 10th	Night	10% 60% 5% 12% 12% 3	1900
	11th to 20th	Night	12% 60% 4 11% 11% 2	1900
	21st to end	Night	15% 59% 4 11% 10% 1	2133
October	1st to 10th	Night	11% 37% 3 12% 34% 3	3800
	11th to 20th	Night	12% 36% 5% 13% 30% 5%	3779
	21st to end	Night	22% 36% 4 16% 18% 3	4120
November	1st to 10th	Night	17% 56% 4 12% 8% 3	2523
	11th to 20th	Night	17% 56% 3 10% 12% 2	2600
	21st to end	Night	22% 56% 4 11% 7%	2790
December	1st to 10th	Night	23% 35% 6% 26% 10%	4580
	11th to 20th	Night	30% 32% 8% 18% 11%	5201
	21st to end	Night	56% 25% 8% 7% 3 1	6996

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	17% 18% 34% 24% 6%	300
	11th to 20th	Day	25% 19% 41% 14% 2	300
	21st to end	Day	18% 20% 41% 19% 3	330
February	1st to 10th	Day	24% 15% 42% 15% 4	300
	11th to 20th	Day	23% 19% 36% 17% 6%	300
	21st to end	Day	21% 17% 42% 16% 4	249
March	1st to 10th	Day	18% 21% 42% 17% 1	300
	11th to 20th	Day	23% 17% 34% 21% 4 1	273
	21st to end	Day	30% 19% 33% 15% 3	378
April	1st to 10th	Day	20% 17% 34% 21% 7% 1	460
	11th to 20th	Day	19% 16% 31% 24% 9% 1	452
	21st to end	Day	21% 12% 37% 22% 7% 1	460
May	1st to 10th	Day	17% 11% 38% 22% 10% 2	553
	11th to 20th	Day	20% 11% 25% 28% 13% 3	675
	21st to end	Day	13% 9% 29% 27% 15% 6%	734
June	1st to 10th	Day	6% 5% 23% 34% 24% 9%	680
	11th to 20th	Day	8% 3 25% 36% 24% 5%	680
	21st to end	Day	9% 7% 30% 34% 18% 3	680
July	1st to 10th	Day	9% 3 16% 34% 25% 13%	671
	11th to 20th	Day	7% 4 19% 38% 25% 7%	668
	21st to end	Day	10% 2 18% 32% 31% 7%	739
August	1st to 10th	Day	7% 2 16% 40% 26% 8%	676
	11th to 20th	Day	9% 2 18% 33% 28% 10%	552
	21st to end	Day	9% 2 14% 32% 32% 12%	539
September	1st to 10th	Day	12% 4 16% 30% 28% 10%	490
	11th to 20th	Day	8% 3 16% 33% 28% 12%	490
	21st to end	Day	9% 7% 23% 31% 20% 10%	405
October	1st to 10th	Day	15% 8% 29% 27% 13% 8%	300
	11th to 20th	Day	13% 21% 31% 24% 10% 1	300
	21st to end	Day	24% 18% 31% 22% 4 1	330
November	1st to 10th	Day	13% 10% 39% 25% 10% 4	300
	11th to 20th	Day	20% 17% 31% 23% 8% 2	300
	21st to end	Day	24% 15% 31% 24% 5% 1	300
December	1st to 10th	Day	13% 13% 46% 19% 6% 4	300
	11th to 20th	Day	18% 19% 36% 23% 4	300
	21st to end	Day	26% 22% 34% 14% 4	330
January	1st to 10th	Night	16% 15% 40% 23% 6%	1000
	11th to 20th	Night	19% 17% 37% 22% 5%	1000
	21st to end	Night	19% 13% 40% 26% 2	1100
February	1st to 10th	Night	21% 13% 39% 24% 3	1000
	11th to 20th	Night	20% 16% 35% 25% 4	885
	21st to end	Night	19% 17% 39% 23% 2	660
March	1st to 10th	Night	19% 15% 41% 21% 4	730
	11th to 20th	Night	21% 11% 34% 29% 5% 1	575
	21st to end	Night	25% 13% 33% 25% 4	627
April	1st to 10th	Night	14% 16% 36% 28% 4	570
	11th to 20th	Night	18% 12% 35% 27% 8%	563
	21st to end	Night	20% 7% 36% 31% 6%	570
May	1st to 10th	Night	15% 8% 34% 34% 8% 1	570
	11th to 20th	Night	16% 6% 28% 36% 13% 1	561
	21st to end	Night	12% 4 27% 34% 21% 2	617
June	1st to 10th	Night	9% 3 21% 42% 25% 2	570
	11th to 20th	Night	10% 2 21% 43% 22% 2	570
	21st to end	Night	6% 2 28% 43% 20% 1	570
July	1st to 10th	Night	10% 3 11% 38% 34% 4	555
	11th to 20th	Night	7% 1 17% 43% 28% 3	552
	21st to end	Night	8% 1 13% 42% 35%	624
August	1st to 10th	Night	5% 2 11% 49% 30% 3	567
	11th to 20th	Night	8% 2 12% 41% 32% 5%	564
	21st to end	Night	6% 1 11% 38% 41% 2	627
September	1st to 10th	Night	12% 2 17% 38% 26% 5%	570
	11th to 20th	Night	8% 3 21% 36% 27% 5%	570
	21st to end	Night	9% 6% 24% 34% 22% 4	722
October	1st to 10th	Night	10% 4 28% 33% 22% 3	760
	11th to 20th	Night	17% 9% 33% 30% 11% 1	760
	21st to end	Night	21% 11% 34% 27% 7%	836
November	1st to 10th	Night	15% 9% 35% 31% 9% 1	780
	11th to 20th	Night	16% 14% 38% 27% 5%	800
	21st to end	Night	23% 11% 36% 24% 6%	990
December	1st to 10th	Night	18% 12% 38% 26% 5% 1	1000
	11th to 20th	Night	24% 10% 34% 27% 6%	1000
	21st to end	Night	25% 16% 33% 23% 3	1100

Page generated at 2025-03-09 07:08:48. Version ac07

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