Tallahassee
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tallahassee clear sky chart from 2005-11-06 to 2024-11-04.

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	10% 6% 2 7% 5% 5% 5% 5% 7% 9% 40%	100904
	Night	10% 6% 2 6% 4 4 5% 4 6% 9% 43%	98051
Transparency	Day	37% 9% 14% 16% 15% 8%	104773
	Night	35% 9% 14% 17% 17% 9%	102321
Seeing	Day	12% 9% 24% 25% 20% 10%	15026
	Night	12% 7% 22% 30% 23% 5%	25009

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	14% 6% 2 6% 4 4 4 2 5% 6% 46%	2836
	11th to 20th	Day	12% 7% 2 6% 4 4 4 4 5% 8% 44%	2848
	21st to end	Day	18% 7% 2 6% 4 4 4 3 5% 7% 40%	3476
February	1st to 10th	Day	16% 7% 2 6% 4 4 5% 3 4 6% 42%	1900
	11th to 20th	Day	16% 6% 2 5% 3 3 4 3 4 6% 48%	1848
	21st to end	Day	15% 6% 2 6% 4 4 3 3 5% 7% 46%	1570
March	1st to 10th	Day	19% 7% 3 7% 4 4 4 3 5% 8% 37%	3266
	11th to 20th	Day	8% 5% 2 6% 5% 4 5% 4 6% 9% 46%	3480
	21st to end	Day	15% 5% 2 4 3 3 4 3 5% 8% 48%	3815
April	1st to 10th	Day	9% 5% 2 6% 5% 4 4 5% 6% 7% 47%	2090
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 6% 6% 47%	2227
	21st to end	Day	6% 4 1 5% 5% 4 4 4 6% 8% 55%	2346
May	1st to 10th	Day	6% 5% 2 5% 5% 4 5% 4 6% 8% 50%	4082
	11th to 20th	Day	12% 7% 2 7% 5% 5% 6% 4 6% 8% 38%	4081
	21st to end	Day	4 3 2 6% 5% 5% 5% 5% 7% 11% 47%	4476
June	1st to 10th	Day	9% 7% 3 8% 6% 7% 7% 6% 8% 10% 28%	2470
	11th to 20th	Day	5% 4 2 8% 7% 9% 8% 7% 10% 10% 29%	2470
	21st to end	Day	7% 6% 3 9% 7% 8% 8% 6% 11% 10% 27%	2470
July	1st to 10th	Day	7% 7% 3 9% 8% 8% 9% 7% 11% 12% 20%	4120
	11th to 20th	Day	5% 4 2 7% 6% 7% 8% 6% 10% 13% 33%	4120
	21st to end	Day	4 5% 2 9% 8% 9% 9% 8% 11% 14% 21%	4466
August	1st to 10th	Day	9% 5% 2 8% 7% 8% 8% 6% 9% 11% 27%	3886
	11th to 20th	Day	6% 5% 3 6% 5% 5% 7% 6% 8% 11% 37%	3729
	21st to end	Day	7% 6% 3 9% 7% 7% 7% 6% 8% 12% 29%	4102
September	1st to 10th	Day	9% 8% 3 10% 6% 7% 8% 5% 8% 11% 26%	2090
	11th to 20th	Day	11% 7% 3 8% 6% 7% 7% 6% 7% 9% 30%	2090
	21st to end	Day	11% 5% 3 6% 3 4 5% 5% 6% 8% 45%	2090
October	1st to 10th	Day	10% 6% 3 7% 4 5% 4 3 5% 6% 47%	2090
	11th to 20th	Day	6% 3 1 5% 3 3 3 3 4 6% 62%	2038
	21st to end	Day	7% 5% 2 6% 3 4 3 3 4 6% 55%	2090
November	1st to 10th	Day	8% 4 2 5% 4 3 3 3 5% 6% 57%	1835
	11th to 20th	Day	10% 5% 1 5% 3 3 3 4 5% 7% 54%	1710
	21st to end	Day	11% 5% 2 6% 5% 4 4 4 5% 5% 48%	1710
December	1st to 10th	Day	13% 6% 3 6% 4 3 4 4 4 7% 46%	1710
	11th to 20th	Day	16% 7% 2 6% 5% 4 3 4 5% 7% 41%	2153
	21st to end	Day	19% 8% 3 6% 4 4 3 2 3 5% 42%	3124
January	1st to 10th	Night	16% 8% 2 7% 4 3 3 3 5% 6% 42%	4109
	11th to 20th	Night	9% 8% 3 6% 4 4 5% 4 5% 7% 45%	4109
	21st to end	Night	19% 10% 3 5% 3 3 3 3 5% 6% 39%	4180
February	1st to 10th	Night	14% 7% 3 6% 5% 3 4 3 5% 6% 45%	2280
	11th to 20th	Night	15% 8% 2 5% 3 3 3 3 4 5% 48%	2218
	21st to end	Night	14% 8% 2 5% 4 3 4 3 4 6% 47%	1884
March	1st to 10th	Night	17% 13% 4 7% 5% 4 4 3 4 7% 34%	3585
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 7% 11% 45%	3480
	21st to end	Night	16% 5% 2 5% 4 3 3 3 5% 7% 46%	3817
April	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 8% 48%	2090
	11th to 20th	Night	10% 4 2 6% 5% 4 4 4 5% 7% 49%	1915
	21st to end	Night	5% 5% 2 4 3 3 3 4 6% 7% 58%	1834
May	1st to 10th	Night	5% 3 2 5% 3 4 4 4 6% 10% 52%	2813
	11th to 20th	Night	10% 6% 2 7% 4 4 4 4 6% 9% 44%	2812
	21st to end	Night	4 4 1 4 3 4 4 4 6% 11% 56%	3079
June	1st to 10th	Night	7% 4 2 6% 5% 4 6% 6% 8% 12% 40%	1710
	11th to 20th	Night	4 5% 3 5% 5% 5% 6% 5% 9% 13% 39%	1710
	21st to end	Night	6% 5% 2 6% 5% 5% 6% 5% 9% 12% 38%	1710
July	1st to 10th	Night	6% 7% 3 8% 7% 7% 8% 7% 10% 12% 24%	2840
	11th to 20th	Night	3 3 2 5% 4 5% 6% 5% 9% 13% 45%	2840
	21st to end	Night	4 4 3 7% 6% 6% 7% 7% 12% 14% 30%	3087
August	1st to 10th	Night	8% 3 2 6% 5% 5% 6% 5% 10% 14% 36%	3038
	11th to 20th	Night	4 3 1 5% 4 6% 5% 6% 10% 15% 41%	3100
	21st to end	Night	7% 7% 3 7% 6% 7% 6% 6% 10% 11% 30%	3508
September	1st to 10th	Night	9% 7% 3 8% 5% 7% 6% 7% 10% 11% 28%	2090
	11th to 20th	Night	9% 7% 3 7% 6% 6% 6% 7% 8% 9% 33%	2090
	21st to end	Night	8% 6% 2 5% 4 4 4 5% 5% 10% 46%	2090
October	1st to 10th	Night	6% 5% 2 6% 5% 5% 4 3 5% 8% 50%	2090
	11th to 20th	Night	6% 4 2 4 3 3 4 3 5% 6% 61%	2140
	21st to end	Night	7% 4 3 5% 4 4 4 3 5% 6% 54%	2508
November	1st to 10th	Night	7% 4 2 6% 4 4 4 3 5% 7% 54%	2311
	11th to 20th	Night	10% 5% 2 4 4 4 3 3 4 6% 54%	2470
	21st to end	Night	13% 6% 2 5% 4 3 4 3 5% 7% 49%	2470
December	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 5% 6% 47%	2470
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 5% 6% 48%	3042
	21st to end	Night	19% 9% 3 6% 4 4 4 3 6% 5% 39%	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	38% 5% 7% 16% 21% 13%	2837
	11th to 20th	Day	34% 8% 8% 15% 17% 18%	2848
	21st to end	Day	43% 6% 7% 13% 21% 11%	3476
February	1st to 10th	Day	42% 7% 7% 15% 18% 11%	1900
	11th to 20th	Day	38% 5% 7% 13% 24% 14%	1858
	21st to end	Day	37% 6% 10% 16% 19% 12%	1570
March	1st to 10th	Day	43% 8% 9% 17% 16% 7%	3266
	11th to 20th	Day	32% 8% 14% 14% 21% 12%	3480
	21st to end	Day	33% 8% 11% 24% 14% 10%	3815
April	1st to 10th	Day	35% 7% 11% 16% 17% 14%	2090
	11th to 20th	Day	35% 6% 9% 19% 19% 11%	2227
	21st to end	Day	25% 7% 12% 22% 22% 11%	2346
May	1st to 10th	Day	27% 11% 15% 21% 19% 7%	4120
	11th to 20th	Day	40% 11% 12% 20% 16% 3	4085
	21st to end	Day	26% 11% 18% 24% 19% 2	4489
June	1st to 10th	Day	45% 13% 17% 17% 7% 1	2470
	11th to 20th	Day	41% 16% 19% 16% 7% 1	2470
	21st to end	Day	44% 15% 21% 13% 6% 2	2470
July	1st to 10th	Day	51% 12% 28% 8% 1	4055
	11th to 20th	Day	39% 12% 34% 13% 2	4051
	21st to end	Day	46% 17% 26% 9% 1	4324
August	1st to 10th	Day	45% 11% 19% 16% 8% 1	3873
	11th to 20th	Day	36% 11% 18% 22% 13%	3765
	21st to end	Day	44% 11% 22% 18% 4 1	4102
September	1st to 10th	Day	47% 14% 17% 14% 7% 2	2090
	11th to 20th	Day	47% 12% 15% 13% 10% 2	2090
	21st to end	Day	36% 7% 15% 20% 15% 8%	2090
October	1st to 10th	Day	44% 5% 6% 10% 18% 17%	3480
	11th to 20th	Day	15% 3 5% 18% 27% 31%	3369
	21st to end	Day	20% 4 5% 15% 38% 18%	3428
November	1st to 10th	Day	27% 5% 9% 19% 24% 17%	1835
	11th to 20th	Day	30% 4 9% 16% 27% 14%	1710
	21st to end	Day	36% 6% 7% 19% 23% 10%	1710
December	1st to 10th	Day	38% 6% 12% 17% 19% 8%	1710
	11th to 20th	Day	41% 6% 8% 14% 20% 10%	2150
	21st to end	Day	46% 3 6% 18% 20% 7%	3124
January	1st to 10th	Night	41% 5% 7% 10% 20% 16%	4109
	11th to 20th	Night	37% 6% 7% 14% 25% 11%	4109
	21st to end	Night	45% 5% 7% 14% 20% 8%	4180
February	1st to 10th	Night	40% 5% 8% 15% 20% 12%	2280
	11th to 20th	Night	39% 5% 8% 13% 20% 15%	2219
	21st to end	Night	38% 6% 9% 17% 15% 15%	1884
March	1st to 10th	Night	49% 8% 10% 13% 13% 7%	3585
	11th to 20th	Night	29% 8% 14% 21% 18% 10%	3480
	21st to end	Night	36% 6% 10% 18% 20% 10%	3817
April	1st to 10th	Night	33% 7% 12% 16% 19% 13%	2090
	11th to 20th	Night	32% 6% 11% 18% 23% 11%	1915
	21st to end	Night	23% 8% 11% 26% 23% 11%	1834
May	1st to 10th	Night	23% 13% 17% 23% 18% 7%	2840
	11th to 20th	Night	33% 11% 16% 23% 14% 3	2813
	21st to end	Night	19% 10% 18% 33% 18% 3	3087
June	1st to 10th	Night	32% 13% 23% 21% 10% 1	1710
	11th to 20th	Night	31% 14% 24% 20% 9% 2	1710
	21st to end	Night	33% 14% 24% 19% 8% 1	1710
July	1st to 10th	Night	49% 15% 25% 9% 2	2795
	11th to 20th	Night	28% 17% 39% 14% 2	2786
	21st to end	Night	37% 19% 31% 11% 2	2988
August	1st to 10th	Night	34% 11% 27% 19% 8%	3027
	11th to 20th	Night	28% 13% 26% 26% 7%	3130
	21st to end	Night	43% 11% 25% 15% 5% 1	3508
September	1st to 10th	Night	42% 16% 19% 13% 8% 2	2090
	11th to 20th	Night	42% 14% 15% 15% 12% 2	2090
	21st to end	Night	32% 10% 16% 19% 16% 8%	2090
October	1st to 10th	Night	41% 6% 9% 12% 18% 14%	3480
	11th to 20th	Night	16% 3 5% 17% 32% 27%	3548
	21st to end	Night	20% 4 5% 16% 38% 17%	4120
November	1st to 10th	Night	29% 5% 8% 19% 20% 17%	2311
	11th to 20th	Night	31% 5% 7% 17% 25% 15%	2470
	21st to end	Night	34% 5% 11% 19% 20% 12%	2470
December	1st to 10th	Night	37% 7% 12% 17% 21% 7%	2470
	11th to 20th	Night	38% 6% 7% 15% 23% 12%	3044
	21st to end	Night	45% 5% 8% 16% 21% 5%	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	15% 23% 44% 14% 3	270
	11th to 20th	Day	14% 17% 38% 22% 6% 2	270
	21st to end	Day	28% 22% 39% 9% 2	297
February	1st to 10th	Day	22% 22% 36% 15% 5%	270
	11th to 20th	Day	24% 18% 39% 17% 2	270
	21st to end	Day	15% 26% 38% 19% 3	225
March	1st to 10th	Day	15% 20% 37% 21% 8%	351
	11th to 20th	Day	16% 16% 36% 20% 10% 1	460
	21st to end	Day	16% 19% 32% 23% 9% 1	506
April	1st to 10th	Day	13% 20% 31% 21% 14% 1	460
	11th to 20th	Day	12% 15% 31% 27% 13% 1	452
	21st to end	Day	8% 12% 30% 32% 15% 3	460
May	1st to 10th	Day	7% 9% 29% 31% 16% 8%	463
	11th to 20th	Day	8% 6% 26% 30% 21% 10%	487
	21st to end	Day	8% 3 19% 34% 22% 13%	529
June	1st to 10th	Day	11% 3 15% 31% 27% 13%	490
	11th to 20th	Day	6% 4 14% 28% 28% 20%	490
	21st to end	Day	8% 3 10% 28% 29% 21%	490
July	1st to 10th	Day	7% 5% 8% 18% 32% 30%	485
	11th to 20th	Day	6% 2 7% 20% 35% 31%	484
	21st to end	Day	5% 2 6% 23% 37% 27%	532
August	1st to 10th	Day	10% 3 9% 22% 32% 24%	486
	11th to 20th	Day	8% 1 6% 20% 38% 28%	479
	21st to end	Day	8% 4 9% 29% 32% 18%	539
September	1st to 10th	Day	12% 3 12% 24% 28% 20%	490
	11th to 20th	Day	14% 2 16% 30% 28% 10%	490
	21st to end	Day	12% 2 15% 23% 34% 14%	490
October	1st to 10th	Day	12% 7% 27% 31% 18% 5%	490
	11th to 20th	Day	6% 6% 25% 36% 21% 6%	490
	21st to end	Day	10% 8% 29% 34% 18% 2	539
November	1st to 10th	Day	13% 9% 26% 31% 18% 3	415
	11th to 20th	Day	13% 14% 45% 20% 6% 1	270
	21st to end	Day	12% 16% 39% 24% 9% 1	270
December	1st to 10th	Day	20% 14% 34% 20% 10% 2	270
	11th to 20th	Day	20% 14% 39% 24% 4	270
	21st to end	Day	23% 11% 32% 27% 6% 1	297
January	1st to 10th	Night	18% 14% 36% 23% 8% 1	760
	11th to 20th	Night	16% 13% 30% 30% 10% 1	760
	21st to end	Night	21% 14% 35% 24% 6%	836
February	1st to 10th	Night	18% 11% 31% 31% 9%	760
	11th to 20th	Night	19% 14% 30% 29% 7%	743
	21st to end	Night	17% 12% 35% 31% 4	628
March	1st to 10th	Night	15% 13% 29% 34% 9%	760
	11th to 20th	Night	14% 12% 30% 31% 13%	760
	21st to end	Night	13% 13% 32% 32% 11%	836
April	1st to 10th	Night	13% 10% 30% 34% 14%	760
	11th to 20th	Night	11% 9% 28% 37% 14% 1	603
	21st to end	Night	6% 6% 28% 37% 21% 1	570
May	1st to 10th	Night	6% 6% 24% 39% 23% 2	570
	11th to 20th	Night	6% 4 23% 37% 25% 5%	561
	21st to end	Night	6% 2 13% 39% 34% 6%	617
June	1st to 10th	Night	7% 2 11% 36% 39% 5%	570
	11th to 20th	Night	5% 2 8% 32% 40% 13%	570
	21st to end	Night	6% 2 7% 29% 43% 13%	570
July	1st to 10th	Night	6% 1 6% 20% 45% 22%	555
	11th to 20th	Night	6% 2 3 16% 47% 26%	552
	21st to end	Night	4 1 3 19% 54% 19%	624
August	1st to 10th	Night	6% 2 6% 20% 48% 18%	567
	11th to 20th	Night	6% 1 4 17% 50% 22%	564
	21st to end	Night	10% 2 9% 25% 38% 17%	646
September	1st to 10th	Night	11% 2 11% 26% 37% 13%	760
	11th to 20th	Night	11% 4 14% 32% 32% 7%	760
	21st to end	Night	8% 3 17% 30% 35% 6%	760
October	1st to 10th	Night	9% 4 25% 31% 28% 3	760
	11th to 20th	Night	7% 5% 24% 35% 25% 3	760
	21st to end	Night	10% 6% 23% 38% 21% 2	836
November	1st to 10th	Night	8% 7% 28% 37% 18% 2	755
	11th to 20th	Night	13% 10% 29% 33% 14% 1	760
	21st to end	Night	14% 9% 28% 36% 13% 1	760
December	1st to 10th	Night	14% 10% 30% 28% 17% 1	760
	11th to 20th	Night	16% 12% 29% 29% 14% 1	760
	21st to end	Night	22% 11% 27% 26% 12% 1	836

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