Maunakea Observatories Forecast
5 PM HST Thursday 08 October (0300 UTC Friday 9 October) 2026
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Warning(s)
Chance for fog/high humidity
Moderate (decreasing) winds
Cloud Cover and Fog/Precipitation Forecast
There is a high risk for periods of fog/high humidity throughout the night; precipitation is unlikely. Patches of mid/upper-level clouds will continue to fill in from the south, passing mainly along the western skies through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 2 C this evening and 2.5 C tomorrow morning. Winds will be from the SW at 20-35 mph for today, easing and switching to a more southerly direction through the night. Seeing and PW will likely be near or exceed 1 arcsecond and 4 mm, respectively, through the night.
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Discussion
The tradewind inversion will remain weak/elevated, likely allowing for more periods of fog and high humidity for tonight and perhaps into tomorrow night. There is a good chance that the inversion will rapidly recover near 6-7 thousand feet by sunrise Saturday, which will allow dry/stable conditions to return to the summit for at least that night. However, more moisture may build in from the east and may raise the stakes on fog/high humidity over the following 2 nights. Nighttime precipitation is unlikely throughout the forecast period. Some afternoon clouds are likely for tomorrow, then will become minimal and short-lived for Saturday, only to pick up again for Sunday and especially early next week.
Patches of deep mid/low-level clouds will continue to build in from the south, passing mainly along the western skies for tonight. The bulk of these clouds will dissipate and/or shift further westward, leaving clear skies overhead for much of the weekend. However, there is still a possibility that patches of deeper clouds will creep in from the east and litter along the northern skies late Saturday night and for Sunday night. There is a chance that these clouds will drift southward and pass along the northern tip of the Big Island for Monday night.
Precipitable water is expected to linger near or exceed 4 mm likely through Friday night, but is set to plummet to 1 mm or less just after sunset on Saturday and through late Sunday morning. There is a chance that PW will rebound back to 1-2 mm through Sunday night and further to 4+ mm for Monday night.
Boundary layer turbulence, moisture, as well as a indistinct inversion will likely contribute to poor/bad seeing for tonight. There is a possibility for a modest improvement in seeing as the atmosphere begins to slowly dry/stabilize and winds subside for Friday evening. However, another round of boundary layer turbulence is expected to degrade seeing again for the remainder of the weekend. There is also a possibility for an increase in free atmospheric turbulence and perhaps another round of moisture/instability, which could limit seeing from improving, despite weaker winds near summit-level, for early next week.
Little change since the morning forecast...A broad/strong low will continue to linger to the NNW of the state before gradually dissipating over the weekend, and eventually lifting northward early next week. While the bulk of the instability/energy will remain contained well to the north, a stream of deep tropical moisture will drift toward the low and over the summit area through at least tonight. This will keep the inversion rather weak/elevated, likely allowing for more fog/high humidity at the summit for tonight. Strong deep southerly flow along the SE flank of the trough/low will promote moderate/strong winds at the summit into early this evening, but winds are set to subside as the low shifts subtly northward as the night progresses. There is a possibility that the stream of moisture flowing out of the tropics will also shift just west of the Big Island through tomorrow, which could help to dry out the air mass over that night. Subsidence associated with a deep ridge to the NE will eventually fill into the area by sunrise Saturday, allowing a distinct inversion to take shape near 6-7 thousand feet, ensuring dry/stable conditions for that night. PW is also set to respond to this deep subsidence and dip toward 0.6-0.8 arcseconds between sunset and at least late Sunday morning. However, a tight mid-level low is expected to develop to the east of the Big Island and drift westward as the weekend progresses. A sharp wind gradient along the western flank of this low is set to fill in overhead, increasing winds near summit-level and thus contributing to another round of boundary layer over much of the weekend. There is a chance that moisture/instability associated with this low will wrap along the northern skies as the weekend progresses and perhaps sag southward around the early part of next week. This could erode the inversion again and increase the risk for fog/high humidity at the summit mainly for Monday night.
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5 Day Forecast Summary (Graphical Trend)
| HST |
Cloud |
Fog/Precip |
Temp |
Wind |
Seeing |
PW |
| Cover (%) |
Height (km) |
Probability (%) |
(Celsius) |
(Dir/MPH) |
(Arcseconds) |
(mm) |
| Thu Oct 08 - 8 PM | 20-40 | 6-8 | 90 / 15 | 2 | SW/20-35 | 0.8-1.6 | 8-12 |
| Fri Oct 09 - 2 AM | 0-20 | 6-7 | 65 / 10 | 2.5 | S/15-30 | 0.7-1.1 | 8-12 |
| 2 PM | 20-40 | 4-5 | 75 / 20 | 6.5 | N/5-15 | NaN | 6-10 |
| 8 PM | 0-10 | Clear | 50 / 10 | 4 | NNE/10-20 | 0.5-0.9 | 4-8 |
| Sat Oct 10 - 2 AM | 0-10 | Clear | 25 / 5 | 4 | N/15-30 | 0.6-1 | 3-5 |
| 2 PM | 0-20 | Clear | 0 / 0 | 9 | N/25-40 | NaN | 1-4 |
| 8 PM | 0-10 | Clear | 0 / 0 | 4 | NNW/35-50 | 1-2 | 0.6-1 |
| Sun Oct 11 - 2 AM | 0-10 | Clear | 0 / 0 | 4 | NNW/35-50 | 0.8-1.6 | 0.6-1 |
| 2 PM | 20-40 | 4-6 | 5 / 0 | 8 | N/20-35 | NaN | 1-2 |
| Mon Oct 12 - 2 AM | 10-30 | 7-8 | 20 / 5 | 2 | NNW/15-30 | 0.7-1.1 | 1-2 |
| 2 PM | 60-80 | 4-8 | 60 / 20 | 6.5 | ESE/10-20 | NaN | 2-4 |
| Tue Oct 13 - 2 AM | 40-60 | 4.5-6 | 65 / 30 | 2 | ENE/5-15 | 0.5-1.1 | 4-8 |
| 2 PM | 70-90 | 4-8 | 75 / 50 | 4.5 | SSW/5-15 | NaN | 8-12 |
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Rise and Set times for the Sun and Moon
| Night (HST) |
Sun Set |
Twilight End |
Twilight Beg |
Sun Rise |
Moon Rise |
Moon Set |
Illumination (%) |
RA |
DEC |
| Thu Oct 08 - Fri Oct 09 |
18:13 |
19:17 |
5:02 |
6:06 |
5:16 |
17:03 |
2 |
12 00.2 |
-3 10 |
| Fri Oct 09 - Sat Oct 10 |
18:12 |
19:16 |
5:02 |
6:06 |
6:10 |
17:39 |
0 |
12 46.7 |
-9 07 |
| Sat Oct 10 - Sun Oct 11 |
18:11 |
19:15 |
5:02 |
6:07 |
7:04 |
18:15 |
1 |
13 33.7 |
-14 36 |
| Sun Oct 11 - Mon Oct 12 |
18:10 |
19:15 |
5:02 |
6:07 |
N/A |
18:53 |
3 |
14 22.1 |
-19 22 |
| Mon Oct 12 - Tue Oct 13 |
18:09 |
19:14 |
5:03 |
6:07 |
N/A |
19:34 |
8 |
15 12.1 |
-23 14 |
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Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 9 October 2026.
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Additional Information
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This message is also available at the MKWC road conditions page.
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