Tampa
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tampa clear sky chart from 2005-11-05 to 2023-05-20.

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	7% 4 2 5% 6% 4 6% 6% 7% 9% 39%	69858
	Night	7% 4 2 5% 5% 3 5% 5% 6% 9% 44%	69407
Transparency	Day	37% 8% 14% 19% 14% 5%	69578
	Night	34% 7% 16% 20% 15% 5%	69197
Seeing	Day	8% 4 17% 26% 24% 18%	13328
	Night	9% 3 19% 33% 26% 8%	23358

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	9% 7% 2 4 4 2 4 5% 5% 10% 44%	1598
	11th to 20th	Day	7% 4 1 4 4 2 4 4 5% 10% 50%	1616
	21st to end	Day	10% 5% 3 6% 4 3 3 5% 4 7% 44%	1889
February	1st to 10th	Day	12% 4 1 5% 4 2 4 4 5% 8% 44%	1776
	11th to 20th	Day	5% 4 1 3 4 2 4 4 4 7% 56%	1717
	21st to end	Day	6% 5% 1 4 5% 2 4 4 4 8% 51%	1517
March	1st to 10th	Day	3 1 1 3 3 3 3 5% 5% 9% 58%	1980
	11th to 20th	Day	6% 3 1 3 4 2 4 4 6% 7% 53%	1947
	21st to end	Day	6% 3 2 4 4 3 3 4 5% 7% 54%	2166
April	1st to 10th	Day	6% 3 2 3 4 2 5% 4 6% 10% 51%	1950
	11th to 20th	Day	7% 4 2 5% 5% 4 5% 5% 6% 9% 42%	1925
	21st to end	Day	3 3 1 4 3 3 5% 6% 6% 9% 53%	2142
May	1st to 10th	Day	4 2 1 2 3 2 3 5% 6% 8% 59%	2328
	11th to 20th	Day	8% 4 1 5% 6% 3 6% 6% 7% 9% 40%	2238
	21st to end	Day	5% 4 2 6% 6% 4 7% 6% 7% 9% 38%	2328
June	1st to 10th	Day	11% 7% 3 6% 6% 5% 7% 8% 8% 10% 25%	2210
	11th to 20th	Day	6% 4 2 6% 8% 4 8% 9% 9% 11% 26%	2210
	21st to end	Day	7% 4 2 7% 8% 5% 9% 7% 8% 12% 24%	2190
July	1st to 10th	Day	8% 5% 2 6% 9% 5% 10% 9% 9% 10% 22%	2210
	11th to 20th	Day	5% 5% 3 8% 8% 5% 8% 8% 9% 10% 23%	2177
	21st to end	Day	5% 5% 3 7% 9% 5% 10% 8% 8% 11% 24%	2376
August	1st to 10th	Day	7% 4 3 8% 8% 6% 7% 9% 10% 9% 23%	2149
	11th to 20th	Day	5% 6% 2 9% 8% 7% 8% 8% 8% 11% 22%	1954
	21st to end	Day	10% 6% 3 7% 8% 6% 8% 8% 9% 9% 23%	2043
September	1st to 10th	Day	6% 6% 2 8% 8% 5% 9% 9% 9% 11% 22%	1861
	11th to 20th	Day	10% 6% 2 8% 7% 5% 7% 7% 7% 10% 25%	1867
	21st to end	Day	6% 7% 1 7% 7% 3 6% 7% 8% 9% 33%	1856
October	1st to 10th	Day	6% 5% 3 6% 6% 4 7% 7% 7% 8% 35%	1863
	11th to 20th	Day	6% 2 2 4 5% 3 6% 5% 5% 8% 48%	1717
	21st to end	Day	6% 4 2 4 4 3 4 5% 6% 10% 47%	1864
November	1st to 10th	Day	7% 4 2 4 5% 3 4 4 5% 7% 49%	1754
	11th to 20th	Day	7% 4 2 5% 5% 3 4 5% 5% 8% 47%	1789
	21st to end	Day	7% 5% 1 5% 5% 3 4 5% 6% 8% 47%	1639
December	1st to 10th	Day	6% 3 2 5% 4 3 5% 5% 5% 10% 47%	1612
	11th to 20th	Day	9% 5% 2 5% 4 3 3 5% 5% 9% 45%	1620
	21st to end	Day	6% 4 2 4 5% 3 5% 6% 7% 9% 43%	1780
January	1st to 10th	Night	8% 5% 2 6% 4 2 5% 5% 5% 8% 44%	2315
	11th to 20th	Night	8% 5% 2 5% 4 3 3 3 6% 9% 47%	2332
	21st to end	Night	12% 5% 3 5% 5% 3 4 4 5% 6% 42%	2385
February	1st to 10th	Night	11% 6% 2 5% 4 2 3 4 5% 7% 46%	2139
	11th to 20th	Night	7% 5% 2 3 4 2 4 4 4 8% 53%	2048
	21st to end	Night	7% 4 3 5% 4 3 4 4 4 7% 48%	1726
March	1st to 10th	Night	4 3 2 3 3 2 3 4 5% 6% 58%	1980
	11th to 20th	Night	6% 3 1 4 4 3 4 4 5% 10% 50%	1959
	21st to end	Night	5% 3 2 3 3 2 4 4 4 7% 56%	2169
April	1st to 10th	Night	5% 2 1 4 4 2 4 4 5% 9% 54%	1959
	11th to 20th	Night	5% 4 2 4 5% 3 4 5% 6% 9% 47%	1922
	21st to end	Night	6% 3 1 4 3 2 4 3 4 8% 57%	1807
May	1st to 10th	Night	2 2 1 3 2 1 4 3 6% 8% 63%	1612
	11th to 20th	Night	6% 4 2 4 4 4 4 5% 7% 9% 45%	1564
	21st to end	Night	5% 3 1 4 4 2 4 4 7% 8% 54%	1601
June	1st to 10th	Night	10% 5% 3 5% 6% 3 6% 5% 6% 10% 35%	1530
	11th to 20th	Night	5% 4 2 5% 6% 2 5% 6% 8% 14% 36%	1530
	21st to end	Night	6% 5% 2 6% 5% 4 7% 7% 8% 12% 33%	1516
July	1st to 10th	Night	6% 4 2 6% 6% 3 6% 9% 8% 13% 30%	1529
	11th to 20th	Night	4 5% 3 4 6% 5% 9% 7% 10% 13% 28%	1509
	21st to end	Night	3 5% 3 7% 8% 4 7% 8% 9% 12% 30%	1640
August	1st to 10th	Night	4 3 2 6% 6% 4 7% 7% 11% 11% 33%	1519
	11th to 20th	Night	4 5% 3 6% 6% 4 6% 8% 9% 12% 32%	1649
	21st to end	Night	8% 7% 3 8% 6% 4 6% 6% 7% 11% 28%	2029
September	1st to 10th	Night	5% 5% 2 7% 8% 5% 7% 8% 9% 12% 27%	1867
	11th to 20th	Night	9% 6% 3 8% 7% 4 6% 6% 7% 11% 28%	1863
	21st to end	Night	7% 7% 2 8% 6% 4 6% 5% 7% 8% 35%	1853
October	1st to 10th	Night	6% 6% 2 5% 6% 3 5% 6% 6% 9% 41%	1866
	11th to 20th	Night	6% 4 1 5% 4 2 4 4 6% 7% 51%	1983
	21st to end	Night	7% 5% 2 6% 4 2 4 3 5% 7% 48%	2237
November	1st to 10th	Night	7% 4 2 3 4 2 4 5% 5% 8% 51%	2094
	11th to 20th	Night	7% 4 2 5% 4 2 4 4 4 6% 52%	2149
	21st to end	Night	6% 4 1 6% 5% 3 4 6% 5% 7% 47%	2292
December	1st to 10th	Night	7% 3 2 4 5% 2 4 4 6% 8% 50%	2328
	11th to 20th	Night	9% 4 2 5% 4 3 4 4 6% 8% 46%	2340
	21st to end	Night	7% 5% 2 5% 4 3 5% 6% 5% 8% 44%	2566

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	34% 4 10% 23% 18% 8%	1601
	11th to 20th	Day	29% 5% 8% 26% 21% 8%	1618
	21st to end	Day	37% 4 7% 17% 24% 8%	1888
February	1st to 10th	Day	35% 5% 9% 20% 18% 10%	1777
	11th to 20th	Day	26% 4 8% 21% 27% 11%	1720
	21st to end	Day	30% 5% 11% 18% 24% 9%	1517
March	1st to 10th	Day	21% 5% 10% 27% 23% 10%	1980
	11th to 20th	Day	26% 6% 10% 27% 19% 9%	1969
	21st to end	Day	27% 5% 9% 25% 24% 8%	2157
April	1st to 10th	Day	27% 6% 15% 23% 19% 7%	1952
	11th to 20th	Day	35% 7% 11% 18% 21% 6%	1926
	21st to end	Day	23% 6% 10% 24% 26% 7%	2142
May	1st to 10th	Day	18% 7% 12% 25% 24% 10%	2327
	11th to 20th	Day	35% 9% 14% 21% 16% 3	2245
	21st to end	Day	36% 9% 11% 21% 18% 2	2328
June	1st to 10th	Day	48% 11% 17% 17% 4	2205
	11th to 20th	Day	42% 13% 20% 19% 3	2210
	21st to end	Day	45% 13% 24% 13% 2	2194
July	1st to 10th	Day	50% 14% 26% 7% 1	2123
	11th to 20th	Day	49% 13% 26% 9%	2090
	21st to end	Day	46% 13% 25% 12% 1	2231
August	1st to 10th	Day	49% 12% 29% 8%	2141
	11th to 20th	Day	50% 14% 23% 10%	1956
	21st to end	Day	52% 12% 22% 11% 1	2045
September	1st to 10th	Day	47% 16% 21% 13% 1	1863
	11th to 20th	Day	49% 11% 21% 12% 5%	1866
	21st to end	Day	41% 9% 14% 20% 10% 3	1856
October	1st to 10th	Day	40% 9% 11% 17% 11% 9%	1863
	11th to 20th	Day	32% 7% 6% 23% 25% 5%	1719
	21st to end	Day	30% 5% 12% 20% 18% 12%	1864
November	1st to 10th	Day	31% 5% 8% 23% 19% 11%	1754
	11th to 20th	Day	33% 6% 7% 21% 21% 9%	1791
	21st to end	Day	33% 5% 9% 22% 21% 7%	1642
December	1st to 10th	Day	32% 4 11% 28% 16% 5%	1618
	11th to 20th	Day	34% 5% 11% 22% 17% 8%	1620
	21st to end	Day	34% 5% 10% 21% 21% 5%	1780
January	1st to 10th	Night	35% 5% 11% 20% 19% 8%	2315
	11th to 20th	Night	33% 4 9% 24% 20% 7%	2332
	21st to end	Night	41% 4 8% 18% 19% 8%	2385
February	1st to 10th	Night	35% 4 10% 18% 20% 9%	2139
	11th to 20th	Night	29% 5% 10% 20% 25% 9%	2056
	21st to end	Night	34% 4 11% 19% 23% 6%	1726
March	1st to 10th	Night	24% 4 11% 28% 23% 8%	1979
	11th to 20th	Night	28% 4 12% 29% 16% 7%	1969
	21st to end	Night	27% 5% 10% 28% 21% 6%	2172
April	1st to 10th	Night	25% 5% 19% 25% 17% 6%	1956
	11th to 20th	Night	31% 6% 13% 23% 20% 5%	1922
	21st to end	Night	25% 4 11% 27% 24% 6%	1807
May	1st to 10th	Night	17% 5% 13% 31% 23% 9%	1615
	11th to 20th	Night	31% 10% 18% 20% 16% 1	1567
	21st to end	Night	26% 7% 19% 23% 21% 1	1602
June	1st to 10th	Night	42% 8% 21% 20% 6%	1524
	11th to 20th	Night	34% 11% 28% 20% 3	1530
	21st to end	Night	40% 12% 27% 14% 5%	1516
July	1st to 10th	Night	41% 16% 30% 9% 1	1476
	11th to 20th	Night	42% 15% 32% 8%	1447
	21st to end	Night	40% 15% 31% 12%	1542
August	1st to 10th	Night	36% 17% 35% 9% 1	1508
	11th to 20th	Night	39% 14% 32% 13%	1649
	21st to end	Night	47% 13% 23% 12% 2	2028
September	1st to 10th	Night	42% 18% 25% 11% 2	1866
	11th to 20th	Night	47% 11% 21% 16% 2	1862
	21st to end	Night	44% 7% 16% 18% 10% 2	1853
October	1st to 10th	Night	35% 10% 13% 18% 13% 7%	1867
	11th to 20th	Night	30% 5% 9% 25% 24% 4	1983
	21st to end	Night	33% 4 11% 19% 20% 10%	2235
November	1st to 10th	Night	29% 4 13% 21% 20% 10%	2094
	11th to 20th	Night	31% 4 10% 21% 22% 8%	2149
	21st to end	Night	33% 5% 8% 25% 18% 8%	2293
December	1st to 10th	Night	30% 4 11% 30% 17% 5%	2332
	11th to 20th	Night	34% 6% 10% 21% 17% 8%	2340
	21st to end	Night	34% 5% 11% 22% 19% 6%	2561

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	10% 11% 40% 28% 8%	240
	11th to 20th	Day	6% 10% 35% 34% 10% 2	240
	21st to end	Day	16% 14% 42% 19% 6%	261
February	1st to 10th	Day	10% 11% 37% 26% 13% 1	240
	11th to 20th	Day	8% 8% 33% 33% 12% 3	240
	21st to end	Day	7% 9% 34% 30% 16% 1	242
March	1st to 10th	Day	4 10% 38% 33% 11%	420
	11th to 20th	Day	11% 7% 27% 32% 19% 1	418
	21st to end	Day	6% 8% 29% 34% 19% 2	462
April	1st to 10th	Day	8% 8% 31% 28% 19% 2	415
	11th to 20th	Day	9% 8% 27% 32% 16% 4	404
	21st to end	Day	5% 6% 23% 31% 27% 6%	417
May	1st to 10th	Day	4 3 19% 37% 24% 9%	422
	11th to 20th	Day	9% 1 16% 30% 27% 15%	443
	21st to end	Day	7% 1 8% 21% 33% 27%	423
June	1st to 10th	Day	14% 1 7% 19% 31% 25%	407
	11th to 20th	Day	7% 3 20% 32% 35%	408
	21st to end	Day	6% 2 13% 27% 49%	405
July	1st to 10th	Day	6% 1 9% 28% 53%	404
	11th to 20th	Day	4 1 13% 34% 45%	399
	21st to end	Day	9% 1 16% 30% 41%	440
August	1st to 10th	Day	8% 2 2 11% 31% 44%	398
	11th to 20th	Day	8% 2 13% 28% 46%	389
	21st to end	Day	10% 2 2 16% 28% 39%	450
September	1st to 10th	Day	9% 1 4 14% 27% 41%	410
	11th to 20th	Day	10% 3 4 23% 29% 27%	409
	21st to end	Day	8% 2 3 22% 36% 26%	406
October	1st to 10th	Day	7% 4 13% 35% 28% 9%	409
	11th to 20th	Day	6% 1 13% 35% 33% 8%	408
	21st to end	Day	8% 4 19% 37% 25% 4	451
November	1st to 10th	Day	10% 4 20% 33% 26% 4	414
	11th to 20th	Day	9% 5% 23% 38% 17% 4	419
	21st to end	Day	6% 5% 28% 38% 18% 2	271
December	1st to 10th	Day	6% 9% 34% 27% 15% 7%	240
	11th to 20th	Day	7% 7% 35% 30% 15% 2	240
	21st to end	Day	6% 9% 25% 40% 14% 3	264
January	1st to 10th	Night	11% 7% 28% 37% 14%	712
	11th to 20th	Night	10% 9% 24% 41% 13%	718
	21st to end	Night	15% 7% 32% 35% 9%	780
February	1st to 10th	Night	15% 5% 29% 34% 15%	707
	11th to 20th	Night	9% 6% 28% 38% 15% 1	688
	21st to end	Night	7% 4 28% 45% 12%	590
March	1st to 10th	Night	5% 5% 36% 40% 10%	719
	11th to 20th	Night	8% 4 29% 40% 16%	712
	21st to end	Night	6% 5% 28% 41% 16%	790
April	1st to 10th	Night	7% 4 27% 41% 17%	712
	11th to 20th	Night	7% 4 33% 38% 14% 1	700
	21st to end	Night	8% 3 26% 42% 18%	697
May	1st to 10th	Night	4 15% 47% 28% 2	538
	11th to 20th	Night	8% 2 14% 40% 29% 4	523
	21st to end	Night	6% 11% 35% 40% 6%	536
June	1st to 10th	Night	11% 7% 26% 43% 9%	506
	11th to 20th	Night	7% 2 17% 46% 25%	507
	21st to end	Night	7% 2 15% 42% 32%	499
July	1st to 10th	Night	8% 1 7% 46% 35%	492
	11th to 20th	Night	6% 1 7% 45% 39%	488
	21st to end	Night	3 2 1 10% 48% 33%	548
August	1st to 10th	Night	5% 11% 48% 33%	496
	11th to 20th	Night	5% 1 7% 41% 42%	496
	21st to end	Night	11% 1 3 18% 37% 27%	727
September	1st to 10th	Night	8% 1 5% 18% 44% 20%	679
	11th to 20th	Night	12% 1 3 27% 39% 14%	676
	21st to end	Night	11% 2 6% 31% 35% 12%	669
October	1st to 10th	Night	10% 2 17% 39% 25% 4	679
	11th to 20th	Night	7% 2 15% 38% 33% 2	674
	21st to end	Night	9% 3 20% 40% 23% 2	745
November	1st to 10th	Night	8% 2 28% 37% 19% 3	698
	11th to 20th	Night	9% 2 24% 41% 20% 1	715
	21st to end	Night	8% 3 26% 44% 16%	717
December	1st to 10th	Night	8% 4 27% 36% 23% 1	717
	11th to 20th	Night	11% 4 22% 40% 19% 1	720
	21st to end	Night	8% 5% 26% 39% 18% 1	788

Page generated at 2023-05-22 06:21:20. Version ac06

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