Mendota Wildlife Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mendota Wildlife Area clear sky chart from 2005-11-05 to 2024-10-14.

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	4 3 1 3 2 2 3 2 4 5% 70%	100821
	Night	6% 3 1 3 3 3 3 2 4 5% 67%	97969
Transparency	Day	17% 5% 8% 17% 25% 28%	100574
	Night	19% 5% 9% 19% 23% 25%	97806
Seeing	Day	5% 4 15% 27% 32% 18%	15287
	Night	6% 3 18% 40% 29% 4	24760

By Month

Percentage Cloud Cover SW (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	10% 10% 4 10% 7% 5% 5% 4 6% 7% 31%	2539
	11th to 20th	Day	9% 8% 4 11% 7% 6% 5% 4 6% 7% 32%	2859
	21st to end	Day	14% 10% 5% 9% 6% 5% 6% 4 6% 7% 29%	3146
February	1st to 10th	Day	12% 5% 2 4 4 4 4 4 5% 7% 48%	1762
	11th to 20th	Day	9% 5% 1 5% 4 3 3 4 5% 7% 54%	1850
	21st to end	Day	11% 5% 2 5% 4 3 4 3 4 6% 52%	1570
March	1st to 10th	Day	7% 5% 3 8% 5% 5% 5% 4 7% 11% 40%	3161
	11th to 20th	Day	6% 3 1 4 3 2 3 2 4 7% 64%	3490
	21st to end	Day	9% 5% 2 5% 4 4 4 4 6% 8% 48%	4031
April	1st to 10th	Day	7% 5% 2 4 3 3 2 2 4 7% 61%	2280
	11th to 20th	Day	5% 3 1 3 3 2 3 3 5% 6% 65%	2249
	21st to end	Day	4 2 1 3 3 2 2 2 4 5% 72%	2280
May	1st to 10th	Day	3 2 1 2 1 1 2 2 2 4 80%	3800
	11th to 20th	Day	1 1 1 1 1 2 1 2 4 85%	4139
	21st to end	Day	2 1 1 1 1 1 1 2 4 85%	4813
June	1st to 10th	Day	2 2 1 2 2 2 2 2 3 6% 77%	2660
	11th to 20th	Day	1 1 1 1 1 1 2 3 90%	2660
	21st to end	Day	1 1 2 1 1 1 1 1 2 88%	2660
July	1st to 10th	Day	1 1 1 2 94%	4420
	11th to 20th	Day	1 1 1 2 1 1 1 2 2 3 85%	4360
	21st to end	Day	1 1 1 1 1 1 2 3 89%	4455
August	1st to 10th	Day	2 1 1 1 1 1 1 2 3 86%	3947
	11th to 20th	Day	1 1 1 1 2 93%	3724
	21st to end	Day	1 1 1 1 1 1 1 1 2 92%	4180
September	1st to 10th	Day	1 1 1 1 1 1 1 1 2 91%	2280
	11th to 20th	Day	1 1 1 1 1 2 1 2 3 86%	2261
	21st to end	Day	1 1 1 1 1 1 2 2 3 3 84%	2090
October	1st to 10th	Day	1 1 1 3 2 1 2 3 3 5% 78%	1924
	11th to 20th	Day	2 2 1 2 1 2 3 2 4 4 77%	1831
	21st to end	Day	3 2 1 3 2 2 3 2 4 6% 71%	1980
November	1st to 10th	Day	5% 3 2 4 3 3 4 3 5% 7% 61%	1715
	11th to 20th	Day	7% 5% 1 4 4 3 4 4 6% 6% 57%	1710
	21st to end	Day	5% 6% 2 6% 3 4 3 3 5% 7% 54%	1710
December	1st to 10th	Day	9% 7% 4 9% 5% 4 4 4 6% 8% 42%	1563
	11th to 20th	Day	16% 8% 3 9% 6% 5% 5% 4 5% 7% 32%	1928
	21st to end	Day	12% 9% 3 8% 6% 5% 6% 4 7% 8% 32%	2794
January	1st to 10th	Night	12% 8% 3 7% 5% 4 4 3 5% 6% 42%	4405
	11th to 20th	Night	12% 7% 3 8% 6% 5% 5% 3 6% 7% 38%	4110
	21st to end	Night	15% 7% 3 7% 4 5% 5% 3 5% 7% 38%	4521
February	1st to 10th	Night	11% 5% 2 3 3 4 3 3 5% 6% 55%	2416
	11th to 20th	Night	8% 3 1 3 3 4 4 3 5% 8% 58%	2218
	21st to end	Night	9% 5% 1 4 3 3 4 2 5% 5% 58%	1884
March	1st to 10th	Night	8% 5% 2 6% 5% 5% 5% 5% 6% 8% 46%	3709
	11th to 20th	Night	6% 4 1 4 3 3 3 3 4 5% 63%	3490
	21st to end	Night	12% 5% 2 5% 4 4 3 3 5% 6% 50%	3620
April	1st to 10th	Night	6% 5% 1 3 2 3 3 3 5% 7% 62%	1900
	11th to 20th	Night	4 2 1 2 3 3 3 2 5% 5% 70%	1879
	21st to end	Night	3 2 2 2 2 2 3 3 7% 75%	1900
May	1st to 10th	Night	1 1 1 1 1 1 1 2 4 85%	3180
	11th to 20th	Night	1 1 1 1 1 1 1 2 4 86%	2753
	21st to end	Night	2 1 1 1 1 1 1 1 1 2 88%	2762
June	1st to 10th	Night	2 2 1 2 2 2 2 2 3 3 79%	1520
	11th to 20th	Night	1 1 1 1 2 3 89%	1520
	21st to end	Night	1 1 1 1 1 2 92%	1520
July	1st to 10th	Night	1 1 1 1 1 2 94%	2540
	11th to 20th	Night	2 1 1 1 1 1 2 1 1 3 86%	2597
	21st to end	Night	1 1 1 2 1 1 2 3 87%	3109
August	1st to 10th	Night	1 1 1 1 1 1 1 3 3 86%	2997
	11th to 20th	Night	1 1 1 1 1 2 1 92%	3126
	21st to end	Night	1 1 1 1 1 1 1 1 2 91%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 1 2 91%	1900
	11th to 20th	Night	2 1 1 2 1 1 1 1 2 2 87%	1919
	21st to end	Night	1 1 1 1 1 1 1 2 3 87%	2090
October	1st to 10th	Night	2 2 2 2 2 2 2 3 4 79%	2251
	11th to 20th	Night	2 2 1 2 1 2 2 3 4 5% 76%	2207
	21st to end	Night	3 1 1 2 1 2 2 2 3 5% 79%	2376
November	1st to 10th	Night	5% 3 1 3 2 3 3 2 4 6% 68%	2362
	11th to 20th	Night	5% 3 1 4 3 2 3 3 4 7% 66%	2470
	21st to end	Night	6% 4 1 3 4 3 3 3 5% 7% 60%	2470
December	1st to 10th	Night	9% 6% 3 6% 4 3 4 3 4 7% 51%	2612
	11th to 20th	Night	12% 7% 3 6% 5% 4 5% 4 7% 9% 38%	3276
	21st to end	Night	12% 7% 3 8% 6% 5% 5% 4 6% 7% 37%	4862

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% 14% 17% 21% 6% 1	2539
	11th to 20th	Day	45% 11% 13% 17% 13% 3	2859
	21st to end	Day	47% 11% 13% 16% 11% 1	3146
February	1st to 10th	Day	31% 7% 11% 26% 17% 7%	1762
	11th to 20th	Day	28% 6% 12% 26% 22% 5%	1860
	21st to end	Day	30% 8% 12% 24% 22% 4	1570
March	1st to 10th	Day	30% 13% 20% 19% 16% 2	3161
	11th to 20th	Day	21% 5% 14% 30% 19% 11%	3490
	21st to end	Day	28% 10% 17% 25% 16% 4	4031
April	1st to 10th	Day	23% 5% 13% 27% 23% 9%	2280
	11th to 20th	Day	20% 4 13% 28% 27% 9%	2252
	21st to end	Day	15% 4 11% 31% 32% 8%	2280
May	1st to 10th	Day	10% 3 7% 23% 37% 21%	3800
	11th to 20th	Day	7% 2 4 20% 45% 22%	4142
	21st to end	Day	7% 2 5% 25% 40% 21%	4814
June	1st to 10th	Day	10% 4 9% 21% 33% 23%	2660
	11th to 20th	Day	4 1 4 14% 39% 37%	2660
	21st to end	Day	6% 1 2 7% 27% 56%	2660
July	1st to 10th	Day	2 1 1 4 12% 81%	4351
	11th to 20th	Day	7% 2 2 5% 16% 68%	4285
	21st to end	Day	4 2 1 5% 28% 59%	4315
August	1st to 10th	Day	7% 1 2 6% 31% 54%	3932
	11th to 20th	Day	3 1 1 5% 27% 64%	3760
	21st to end	Day	4 1 2 7% 29% 57%	4179
September	1st to 10th	Day	4 1 2 7% 28% 57%	2280
	11th to 20th	Day	6% 2 3 18% 42% 29%	2261
	21st to end	Day	7% 2 3 17% 39% 31%	2090
October	1st to 10th	Day	10% 3 6% 19% 30% 32%	1924
	11th to 20th	Day	11% 3 5% 25% 30% 25%	1831
	21st to end	Day	15% 4 7% 22% 31% 21%	1980
November	1st to 10th	Day	21% 5% 11% 25% 27% 10%	1715
	11th to 20th	Day	23% 8% 14% 26% 25% 4	1710
	21st to end	Day	26% 6% 12% 24% 24% 8%	1710
December	1st to 10th	Day	37% 8% 11% 19% 18% 8%	1563
	11th to 20th	Day	49% 8% 11% 18% 11% 3	1928
	21st to end	Day	40% 14% 17% 18% 9% 1	2794
January	1st to 10th	Night	36% 12% 16% 26% 10% 1	4405
	11th to 20th	Night	40% 10% 15% 19% 10% 6%	4110
	21st to end	Night	41% 10% 14% 19% 13% 3	4521
February	1st to 10th	Night	29% 6% 10% 25% 22% 8%	2416
	11th to 20th	Night	23% 6% 11% 26% 27% 7%	2219
	21st to end	Night	26% 6% 12% 28% 23% 6%	1884
March	1st to 10th	Night	28% 12% 19% 19% 18% 4	3709
	11th to 20th	Night	20% 6% 13% 28% 23% 10%	3490
	21st to end	Night	29% 9% 17% 26% 14% 5%	3620
April	1st to 10th	Night	22% 5% 14% 29% 21% 9%	1900
	11th to 20th	Night	16% 4 12% 31% 28% 10%	1879
	21st to end	Night	12% 4 10% 31% 34% 9%	1900
May	1st to 10th	Night	6% 3 7% 28% 33% 23%	3180
	11th to 20th	Night	6% 2 4 20% 45% 25%	2754
	21st to end	Night	7% 2 4 25% 45% 18%	2762
June	1st to 10th	Night	11% 2 8% 20% 33% 25%	1520
	11th to 20th	Night	4 2 4 15% 36% 39%	1520
	21st to end	Night	3 1 1 7% 27% 60%	1520
July	1st to 10th	Night	2 1 1 2 12% 82%	2500
	11th to 20th	Night	6% 2 2 4 13% 74%	2549
	21st to end	Night	4 2 2 5% 23% 64%	3011
August	1st to 10th	Night	6% 1 1 6% 23% 62%	2988
	11th to 20th	Night	3 1 2 4 19% 71%	3156
	21st to end	Night	5% 1 1 7% 25% 62%	3498
September	1st to 10th	Night	5% 1 2 6% 24% 63%	1900
	11th to 20th	Night	7% 2 2 15% 39% 35%	1919
	21st to end	Night	6% 1 3 14% 39% 37%	2090
October	1st to 10th	Night	12% 3 6% 18% 25% 37%	2251
	11th to 20th	Night	10% 4 6% 21% 30% 29%	2207
	21st to end	Night	10% 2 5% 22% 34% 26%	2376
November	1st to 10th	Night	17% 5% 9% 25% 29% 15%	2362
	11th to 20th	Night	18% 5% 13% 25% 31% 8%	2470
	21st to end	Night	22% 5% 10% 24% 29% 10%	2470
December	1st to 10th	Night	31% 7% 11% 23% 18% 11%	2612
	11th to 20th	Night	39% 11% 13% 19% 15% 3	3276
	21st to end	Night	40% 11% 17% 19% 10% 3	4862

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	20% 9% 17% 31% 16% 7%	180
	11th to 20th	Day	9% 5% 18% 29% 26% 13%	369
	21st to end	Day	12% 4 18% 22% 27% 17%	407
February	1st to 10th	Day	13% 6% 20% 21% 21% 19%	394
	11th to 20th	Day	9% 9% 18% 32% 18% 15%	455
	21st to end	Day	8% 10% 22% 29% 24% 7%	382
March	1st to 10th	Day	11% 8% 19% 32% 23% 6%	460
	11th to 20th	Day	9% 8% 21% 28% 23% 10%	460
	21st to end	Day	11% 11% 23% 29% 18% 8%	506
April	1st to 10th	Day	8% 8% 26% 25% 20% 12%	460
	11th to 20th	Day	6% 8% 25% 31% 18% 11%	452
	21st to end	Day	3 7% 25% 30% 20% 15%	460
May	1st to 10th	Day	3 7% 22% 34% 25% 9%	463
	11th to 20th	Day	2 5% 18% 32% 30% 13%	488
	21st to end	Day	4 6% 16% 26% 31% 18%	529
June	1st to 10th	Day	1 4 14% 31% 32% 17%	490
	11th to 20th	Day	1 2 18% 29% 37% 13%	490
	21st to end	Day	1 10% 28% 40% 21%	490
July	1st to 10th	Day	1 6% 24% 45% 24%	486
	11th to 20th	Day	1 1 17% 46% 36%	484
	21st to end	Day	1 2 19% 49% 29%	531
August	1st to 10th	Day	3 1 5% 24% 44% 23%	487
	11th to 20th	Day	1 7% 25% 42% 24%	477
	21st to end	Day	1 4 23% 43% 29%	539
September	1st to 10th	Day	1 1 5% 26% 47% 21%	490
	11th to 20th	Day	2 2 11% 36% 34% 15%	490
	21st to end	Day	1 2 12% 25% 40% 20%	490
October	1st to 10th	Day	1 3 17% 27% 31% 20%	490
	11th to 20th	Day	2 4 13% 27% 33% 22%	463
	21st to end	Day	3 4 13% 23% 35% 23%	495
November	1st to 10th	Day	6% 2 15% 22% 33% 23%	311
	11th to 20th	Day	3 4 12% 27% 31% 22%	270
	21st to end	Day	8% 1 14% 29% 34% 14%	270
December	1st to 10th	Day	11% 3 21% 25% 27% 12%	201
	11th to 20th	Day	10% 7% 14% 31% 23% 16%	180
	21st to end	Day	15% 10% 20% 23% 25% 7%	198
January	1st to 10th	Night	16% 4 14% 34% 27% 6%	760
	11th to 20th	Night	9% 3 13% 38% 32% 6%	760
	21st to end	Night	13% 2 14% 36% 32% 4	836
February	1st to 10th	Night	12% 4 14% 35% 29% 6%	760
	11th to 20th	Night	9% 5% 18% 33% 31% 5%	744
	21st to end	Night	10% 6% 18% 42% 22% 3	628
March	1st to 10th	Night	10% 5% 20% 40% 23% 3	760
	11th to 20th	Night	8% 6% 20% 34% 28% 4	760
	21st to end	Night	8% 6% 26% 38% 20% 2	836
April	1st to 10th	Night	6% 6% 29% 36% 21% 2	760
	11th to 20th	Night	4 8% 29% 35% 21% 3	751
	21st to end	Night	3 5% 30% 38% 20% 4	760
May	1st to 10th	Night	2 4 31% 40% 20% 3	760
	11th to 20th	Night	2 4 31% 47% 17%	520
	21st to end	Night	3 6% 29% 46% 16%	411
June	1st to 10th	Night	3 4 33% 46% 14% 1	380
	11th to 20th	Night	4 26% 52% 18% 1	380
	21st to end	Night	1 1 22% 55% 20% 1	380
July	1st to 10th	Night	18% 53% 28%	370
	11th to 20th	Night	2 10% 58% 30% 1	399
	21st to end	Night	1 10% 44% 42% 3	624
August	1st to 10th	Night	2 15% 49% 31% 3	651
	11th to 20th	Night	1 13% 48% 36% 2	752
	21st to end	Night	1 10% 42% 45% 3	836
September	1st to 10th	Night	1 1 9% 46% 40% 4	760
	11th to 20th	Night	1 1 17% 44% 31% 5%	760
	21st to end	Night	1 1 14% 37% 41% 6%	760
October	1st to 10th	Night	3 3 15% 39% 34% 6%	760
	11th to 20th	Night	3 1 14% 34% 39% 8%	734
	21st to end	Night	4 3 11% 32% 37% 15%	792
November	1st to 10th	Night	5% 3 13% 32% 38% 10%	740
	11th to 20th	Night	5% 1 11% 40% 35% 8%	760
	21st to end	Night	7% 2 13% 37% 34% 7%	760
December	1st to 10th	Night	11% 3 13% 36% 31% 5%	760
	11th to 20th	Night	13% 4 14% 39% 26% 4	760
	21st to end	Night	13% 6% 15% 40% 22% 3	836

Page generated at 2024-10-11 07:49:59. Version ac07

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