Rome
Clear Sky Chart
History

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

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	15% 9% 3 7% 4 4 4 4 5% 7% 36%	101171
	Night	15% 10% 3 7% 4 4 4 3 5% 7% 37%	97956
Transparency	Day	25% 45% 6% 14% 9% 1	104902
	Night	25% 46% 5% 14% 9% 1	102363
Seeing	Day	22% 13% 27% 21% 12% 5%	14846
	Night	20% 11% 25% 27% 15% 2	24902

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	17% 18% 6% 11% 4 4 3 4 5% 6% 23%	2836
	11th to 20th	Day	17% 15% 7% 15% 6% 5% 3 2 3 4 24%	2840
	21st to end	Day	27% 19% 6% 7% 4 3 3 3 4 4 20%	3124
February	1st to 10th	Day	20% 13% 5% 10% 5% 3 4 3 4 4 29%	1757
	11th to 20th	Day	18% 12% 5% 9% 4 5% 4 4 5% 5% 30%	1848
	21st to end	Day	20% 14% 4 7% 3 3 3 3 5% 5% 32%	1570
March	1st to 10th	Day	21% 16% 4 8% 4 4 3 3 4 5% 27%	3241
	11th to 20th	Day	15% 7% 3 6% 5% 4 4 4 5% 7% 41%	3480
	21st to end	Day	17% 9% 3 6% 5% 4 4 3 6% 7% 35%	3815
April	1st to 10th	Day	15% 11% 3 7% 4 4 4 3 5% 6% 38%	2148
	11th to 20th	Day	18% 9% 3 6% 4 4 4 4 4 7% 39%	2352
	21st to end	Day	17% 9% 3 7% 5% 5% 5% 3 5% 7% 36%	2470
May	1st to 10th	Day	21% 10% 3 8% 4 4 5% 4 5% 6% 30%	4082
	11th to 20th	Day	21% 9% 3 7% 4 4 4 3 5% 8% 33%	4081
	21st to end	Day	11% 7% 3 7% 5% 6% 6% 5% 8% 9% 34%	4476
June	1st to 10th	Day	12% 5% 1 6% 5% 5% 6% 6% 6% 8% 40%	2470
	11th to 20th	Day	10% 5% 2 7% 5% 6% 6% 4 6% 8% 41%	2470
	21st to end	Day	10% 6% 2 6% 6% 5% 5% 5% 7% 9% 39%	2470
July	1st to 10th	Day	12% 6% 3 7% 4 5% 6% 4 5% 9% 40%	4120
	11th to 20th	Day	8% 5% 2 5% 5% 5% 6% 5% 7% 10% 42%	4120
	21st to end	Day	13% 11% 3 9% 6% 6% 5% 5% 7% 8% 28%	4466
August	1st to 10th	Day	8% 5% 2 7% 5% 5% 6% 4 7% 11% 40%	4104
	11th to 20th	Day	9% 6% 3 6% 5% 5% 6% 4 7% 10% 38%	4044
	21st to end	Day	6% 4 1 5% 4 4 4 4 6% 8% 55%	4326
September	1st to 10th	Day	14% 5% 2 5% 3 4 4 4 4 6% 48%	2104
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 5% 7% 49%	2090
	21st to end	Day	18% 7% 2 7% 3 3 4 3 4 6% 43%	2090
October	1st to 10th	Day	12% 5% 1 5% 3 4 4 3 6% 7% 50%	2071
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 4 6% 47%	1900
	21st to end	Day	20% 8% 2 6% 3 3 4 3 4 6% 41%	2037
November	1st to 10th	Day	13% 7% 2 5% 3 4 3 3 5% 6% 51%	1762
	11th to 20th	Day	14% 13% 3 6% 4 3 3 4 4 6% 39%	1710
	21st to end	Day	18% 9% 3 6% 4 4 4 3 5% 6% 38%	1710
December	1st to 10th	Day	24% 14% 4 8% 5% 4 4 3 4 5% 26%	1710
	11th to 20th	Day	17% 15% 6% 8% 4 4 4 3 4 5% 28%	2153
	21st to end	Day	19% 19% 5% 10% 6% 4 4 3 5% 5% 20%	3124
January	1st to 10th	Night	15% 20% 6% 11% 5% 5% 5% 3 5% 4 21%	4109
	11th to 20th	Night	19% 16% 6% 13% 5% 4 3 3 4 4 25%	4120
	21st to end	Night	25% 16% 5% 8% 4 4 3 2 4 4 24%	4532
February	1st to 10th	Night	21% 13% 4 9% 5% 4 3 3 5% 5% 28%	2420
	11th to 20th	Night	21% 13% 3 9% 4 5% 4 3 4 5% 31%	2218
	21st to end	Night	23% 14% 4 8% 4 3 3 2 4 5% 29%	1884
March	1st to 10th	Night	21% 14% 3 6% 4 3 4 3 4 5% 32%	3610
	11th to 20th	Night	14% 9% 2 6% 4 3 4 4 5% 7% 42%	3480
	21st to end	Night	14% 9% 3 7% 5% 4 5% 4 5% 6% 38%	3817
April	1st to 10th	Night	15% 9% 3 6% 5% 4 4 4 6% 8% 38%	2047
	11th to 20th	Night	15% 8% 3 6% 4 4 4 4 6% 6% 41%	1775
	21st to end	Night	16% 8% 3 6% 4 4 4 4 5% 6% 38%	1710
May	1st to 10th	Night	24% 11% 3 7% 4 4 4 3 4 7% 29%	2813
	11th to 20th	Night	20% 8% 2 6% 4 3 4 3 5% 7% 38%	2812
	21st to end	Night	11% 5% 2 6% 4 5% 4 4 7% 9% 44%	3079
June	1st to 10th	Night	8% 5% 2 5% 5% 5% 5% 5% 7% 8% 46%	1710
	11th to 20th	Night	6% 5% 1 6% 4 4 5% 4 7% 11% 46%	1710
	21st to end	Night	7% 5% 2 5% 4 4 5% 5% 7% 11% 45%	1710
July	1st to 10th	Night	8% 6% 2 6% 4 4 4 4 6% 9% 45%	2840
	11th to 20th	Night	6% 6% 2 6% 5% 5% 5% 3 7% 10% 45%	2840
	21st to end	Night	11% 10% 3 7% 5% 5% 4 5% 6% 8% 36%	3087
August	1st to 10th	Night	8% 6% 2 8% 4 5% 5% 4 7% 9% 43%	2825
	11th to 20th	Night	9% 7% 3 7% 4 5% 5% 4 5% 8% 43%	2785
	21st to end	Night	4 3 1 4 3 4 3 4 6% 9% 59%	3313
September	1st to 10th	Night	11% 5% 2 4 3 4 4 4 5% 8% 51%	2057
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 4 6% 54%	2090
	21st to end	Night	13% 6% 2 6% 4 3 4 4 5% 6% 47%	2090
October	1st to 10th	Night	10% 5% 2 5% 3 4 4 3 5% 7% 53%	2108
	11th to 20th	Night	14% 6% 2 5% 3 3 5% 4 5% 8% 45%	2280
	21st to end	Night	19% 8% 2 6% 4 4 4 3 4 5% 42%	2558
November	1st to 10th	Night	13% 7% 2 5% 4 3 3 3 5% 6% 49%	2536
	11th to 20th	Night	16% 9% 4 7% 4 4 4 3 4 6% 39%	2477
	21st to end	Night	18% 13% 3 6% 4 4 3 3 4 5% 37%	2470
December	1st to 10th	Night	22% 13% 4 8% 4 4 3 3 5% 6% 27%	2470
	11th to 20th	Night	18% 12% 7% 9% 4 3 3 3 4 6% 31%	3042
	21st to end	Night	19% 18% 5% 10% 6% 5% 4 3 4 5% 19%	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	41% 36% 8% 8% 7%	2837
	11th to 20th	Day	44% 36% 4 12% 4	2840
	21st to end	Day	46% 38% 2 11% 2	3124
February	1st to 10th	Day	22% 64% 3 6% 5%	1757
	11th to 20th	Day	21% 63% 2 8% 6%	1858
	21st to end	Day	18% 64% 2 9% 6% 1	1570
March	1st to 10th	Day	41% 39% 4 10% 5% 2	3241
	11th to 20th	Day	21% 39% 7% 20% 12%	3480
	21st to end	Day	26% 40% 5% 18% 10% 1	3815
April	1st to 10th	Day	20% 64% 3 9% 3	2148
	11th to 20th	Day	16% 65% 4 9% 5% 1	2352
	21st to end	Day	16% 64% 5% 9% 4 1	2470
May	1st to 10th	Day	35% 40% 6% 14% 5%	4120
	11th to 20th	Day	30% 39% 7% 16% 8%	4085
	21st to end	Day	28% 40% 8% 12% 10% 2	4489
June	1st to 10th	Day	15% 65% 4 8% 7%	2470
	11th to 20th	Day	15% 65% 5% 8% 6%	2470
	21st to end	Day	15% 63% 5% 9% 6% 1	2470
July	1st to 10th	Day	28% 37% 9% 16% 10% 1	4055
	11th to 20th	Day	21% 36% 7% 26% 9%	4051
	21st to end	Day	40% 35% 6% 9% 9% 1	4324
August	1st to 10th	Day	24% 37% 10% 24% 5%	4091
	11th to 20th	Day	24% 37% 6% 22% 10%	4083
	21st to end	Day	14% 37% 11% 22% 15% 1	4325
September	1st to 10th	Day	13% 60% 6% 9% 9% 3	2104
	11th to 20th	Day	13% 59% 5% 12% 9% 1	2090
	21st to end	Day	17% 59% 4 13% 8%	2090
October	1st to 10th	Day	13% 36% 4 20% 27% 1	3448
	11th to 20th	Day	15% 36% 5% 20% 22% 1	3140
	21st to end	Day	17% 36% 7% 19% 18% 2	3339
November	1st to 10th	Day	20% 55% 4 13% 7% 1	1762
	11th to 20th	Day	17% 59% 3 9% 11% 2	1710
	21st to end	Day	21% 59% 5% 12% 4	1710
December	1st to 10th	Day	27% 59% 3 7% 4	1710
	11th to 20th	Day	30% 47% 3 11% 8% 1	2150
	21st to end	Day	46% 36% 4 9% 4 1	3124
January	1st to 10th	Night	45% 36% 4 9% 6%	4109
	11th to 20th	Night	42% 36% 3 14% 5% 1	4120
	21st to end	Night	42% 38% 3 12% 4 1	4532
February	1st to 10th	Night	21% 64% 3 7% 4 1	2420
	11th to 20th	Night	21% 63% 2 8% 5%	2219
	21st to end	Night	21% 64% 3 7% 5% 1	1884
March	1st to 10th	Night	37% 40% 3 15% 4 1	3610
	11th to 20th	Night	21% 39% 5% 21% 13%	3480
	21st to end	Night	27% 40% 4 18% 11%	3817
April	1st to 10th	Night	18% 65% 4 8% 5%	2047
	11th to 20th	Night	16% 65% 3 10% 6% 1	1775
	21st to end	Night	17% 64% 4 8% 6% 1	1710
May	1st to 10th	Night	37% 40% 5% 13% 5% 1	2840
	11th to 20th	Night	27% 40% 8% 19% 5%	2813
	21st to end	Night	22% 40% 7% 18% 10% 3	3087
June	1st to 10th	Night	14% 65% 4 9% 7% 1	1710
	11th to 20th	Night	12% 65% 5% 7% 9% 1	1710
	21st to end	Night	13% 64% 7% 10% 6% 1	1710
July	1st to 10th	Night	23% 38% 9% 16% 12% 2	2795
	11th to 20th	Night	23% 37% 8% 21% 11%	2786
	21st to end	Night	34% 36% 6% 12% 10% 3	2988
August	1st to 10th	Night	25% 37% 10% 22% 4 1	2814
	11th to 20th	Night	28% 38% 5% 17% 12%	2812
	21st to end	Night	11% 36% 12% 24% 15% 1	3313
September	1st to 10th	Night	11% 60% 6% 12% 8% 3	2057
	11th to 20th	Night	13% 59% 4 10% 12% 1	2090
	21st to end	Night	14% 59% 5% 12% 10%	2090
October	1st to 10th	Night	13% 36% 4 17% 28% 1	3511
	11th to 20th	Night	12% 36% 5% 17% 26% 3	3779
	21st to end	Night	17% 36% 5% 16% 20% 7%	4206
November	1st to 10th	Night	21% 55% 4 11% 7% 1	2536
	11th to 20th	Night	19% 59% 2 8% 10% 2	2477
	21st to end	Night	22% 59% 4 12% 4	2470
December	1st to 10th	Night	25% 59% 3 7% 5% 1	2470
	11th to 20th	Night	29% 48% 3 13% 7% 1	3044
	21st to end	Night	46% 36% 4 9% 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	30% 23% 33% 10% 3	270
	11th to 20th	Day	39% 25% 27% 9%	270
	21st to end	Day	33% 27% 29% 10% 1	297
February	1st to 10th	Day	33% 25% 27% 13% 3	270
	11th to 20th	Day	37% 27% 29% 4 2	270
	21st to end	Day	37% 21% 36% 6%	225
March	1st to 10th	Day	36% 21% 29% 11% 3	339
	11th to 20th	Day	29% 22% 31% 12% 5%	460
	21st to end	Day	35% 18% 30% 13% 5%	506
April	1st to 10th	Day	31% 18% 26% 17% 7% 1	460
	11th to 20th	Day	27% 18% 29% 17% 6% 3	452
	21st to end	Day	25% 20% 34% 14% 5% 2	460
May	1st to 10th	Day	25% 20% 30% 15% 8% 2	463
	11th to 20th	Day	23% 11% 30% 22% 10% 4	487
	21st to end	Day	16% 10% 25% 26% 14% 8%	529
June	1st to 10th	Day	14% 8% 25% 30% 16% 6%	490
	11th to 20th	Day	11% 7% 29% 30% 16% 7%	490
	21st to end	Day	12% 10% 29% 26% 14% 9%	490
July	1st to 10th	Day	14% 6% 19% 22% 20% 19%	485
	11th to 20th	Day	10% 6% 24% 31% 20% 10%	484
	21st to end	Day	14% 5% 22% 28% 21% 10%	532
August	1st to 10th	Day	12% 5% 20% 30% 20% 12%	486
	11th to 20th	Day	14% 5% 21% 32% 20% 8%	479
	21st to end	Day	9% 5% 16% 32% 26% 12%	539
September	1st to 10th	Day	14% 6% 17% 26% 27% 9%	490
	11th to 20th	Day	11% 4 19% 29% 27% 10%	490
	21st to end	Day	24% 7% 21% 26% 18% 4	490
October	1st to 10th	Day	14% 6% 27% 31% 18% 6%	490
	11th to 20th	Day	18% 14% 32% 20% 11% 4	490
	21st to end	Day	23% 14% 34% 21% 8%	486
November	1st to 10th	Day	20% 13% 37% 20% 7% 2	300
	11th to 20th	Day	31% 17% 30% 17% 4 1	270
	21st to end	Day	27% 18% 35% 16% 3 1	270
December	1st to 10th	Day	32% 20% 30% 11% 6%	270
	11th to 20th	Day	26% 23% 33% 14% 3	270
	21st to end	Day	33% 24% 32% 9% 1	297
January	1st to 10th	Night	30% 19% 31% 17% 4	760
	11th to 20th	Night	34% 19% 29% 15% 2	760
	21st to end	Night	27% 20% 30% 21% 2	836
February	1st to 10th	Night	31% 17% 31% 20% 1	760
	11th to 20th	Night	32% 21% 29% 17% 1	743
	21st to end	Night	34% 19% 31% 15% 1	628
March	1st to 10th	Night	28% 16% 31% 20% 4	760
	11th to 20th	Night	27% 18% 30% 19% 6% 1	760
	21st to end	Night	23% 16% 32% 22% 7%	836
April	1st to 10th	Night	23% 15% 32% 22% 7%	717
	11th to 20th	Night	20% 12% 33% 25% 10% 1	563
	21st to end	Night	18% 12% 37% 25% 7% 1	570
May	1st to 10th	Night	21% 11% 29% 25% 11% 2	570
	11th to 20th	Night	19% 8% 24% 32% 16% 1	561
	21st to end	Night	10% 5% 21% 34% 25% 5%	617
June	1st to 10th	Night	8% 6% 22% 41% 22% 2	570
	11th to 20th	Night	8% 3 21% 36% 28% 4	570
	21st to end	Night	8% 5% 23% 35% 26% 3	570
July	1st to 10th	Night	13% 2 16% 28% 32% 9%	555
	11th to 20th	Night	6% 3 13% 40% 33% 5%	552
	21st to end	Night	10% 4 13% 37% 31% 4	624
August	1st to 10th	Night	8% 2 10% 40% 33% 6%	567
	11th to 20th	Night	9% 3 10% 39% 31% 7%	564
	21st to end	Night	8% 1 13% 34% 37% 7%	627
September	1st to 10th	Night	13% 3 11% 33% 34% 6%	727
	11th to 20th	Night	13% 3 16% 30% 32% 7%	760
	21st to end	Night	14% 7% 21% 33% 23% 2	760
October	1st to 10th	Night	13% 6% 21% 32% 25% 4	760
	11th to 20th	Night	18% 11% 27% 28% 15% 1	760
	21st to end	Night	22% 13% 25% 27% 12% 1	836
November	1st to 10th	Night	18% 12% 25% 27% 16% 1	780
	11th to 20th	Night	23% 15% 28% 24% 8% 1	763
	21st to end	Night	26% 13% 25% 26% 9% 1	760
December	1st to 10th	Night	30% 19% 24% 22% 5%	760
	11th to 20th	Night	25% 17% 30% 21% 6% 1	760
	21st to end	Night	31% 17% 30% 20% 3	836

Page generated at 2024-11-08 06:44:48. Version ac07

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